NormalMan

For me, and I would assume for many people, the fun of the game comes from the risk and terror of the fight and flight to survive. That's why late game, if you survive that far, starts to become a bit stale. It all becomes a little too safe and you have the option to just play it as a base building/farming game. No real challenge.
 
So my solution is to make the game much harder so that surviving to late game is quite unlikely, and while you are alive, there's more challenge, more fear, and more problems. Putting zombie type onto random so you never know if the zombie near you is shambler, fast shambler, or sprinter is one way to keep things exciting. And then play with house alarms and car alarms on thus making even zombies not attracted to you sources of second degree danger. If you're especially masochistic, play with the helicopter event as Sometimes. Since there isn't really a robust event system (like in Rimworld), this will absolutely remove any complacency which increases fun and interest.

I liked the idea of wandering traders a lot. Late game should not only be about zombie populations but also about survivors forming bigger and better groups. Dynamic content in the form of quests you give to or receive from survivors. Maybe even a community establishing itself and dealing with hordes, the breaking down of technology and the scarcity of certain items such as ammo and medicine.
 
Having options to improve player structures, player vehicles, clothes, better food storage etc. would also provide a lot of late game fun for me.

In the long dark the world runs out of manufactured resources which means you end up having to use bows, hand forged knives/axes, you have to hunt your own food and survive wildlife encounters with wolves, bears, and moose without access to flare guns, rifles, or revolvers. You have to render fish oil in order to use a storm lantern after you exhaust all the jerry cans. You would have to handload your own ammunition, or start using black powder guns which you can very easily cast your own lead for and use gunpowder for. 
 
As for zombies;
They would starve and die off over time, the fit ones would cannibalize other zombies and they would become more fit for survival. The parasite in their heads would make their hosts more fit for survival rather. I would expect zombies to start using tactics used by animals like foraging for food, stealing from traps, depleting your reserves of food. I would expect them to be able to run, or make vocalizations to draw many more zombies to them. They would not increase in population however in prolonged periods. The ones that starve and die en masse would end up poisoning the air and you would need a respirator to live in those areas. Corpse disposal is not important enough in game. You would need to get a full face respirator along with in date filters for it to not die of severe infection entering areas littered with corpses. 40mm nato filters CAN be improvised if you have charcoal and fine enough cotton to put together a filter. Activated charcoal is commonly used in the medical industry, and it is used in gas mask filters.  Wearing a gasmask increases exertion, decreases your perception radius, and most masks don't allow you to drink, only the military masks really have standardized drinking tubes.   Due to the zombies becoming more adaptive, melee would be absolute suicide, melee shouldn't be as effective as it is with weapons that don't allow you to reach a human skull outside an arms reach. Late game when zombies are faster and smarter, and potentially capable grabbing your weapon, ranged weapons need to be learned. Clearing them by having them walk into a campfire won't work as they've learned that hot stuff burns.  Wildlife;
Wild boars would make you miserable. They would destroy your crops, steal from your traps, forage from your forests, and draw zombies to themselves and thus, to your supplies. They would fight with zombies and I would guess be immune, or they could eat/bite/impale zombies and become carriers so if they impale/bite you, you risk zombification. They could also try to drink from your water collectors and damage them. Wild boars would make the apocalypse worse than zombies ever could once you are living off the land. If you can hunt them effectively, you've a renewable supply of BACON! People hunt wild hogs in the south with 50 round drums and thermal scopes from trucks because they are such a massive problem ravaging farms with herds in the dozens.  They could eat zombies which means tainted boars could not be safely eaten or used as bait for traps, plus they would infect you. Urban boar populations would be magnitudes worse than zombies given they can charge and you won't be killing them by bashing their skulls. You'd have to hunt boars out in the sticks to get usable carcasses. These boars would move in to feast on the rotting zombies. Rotting food in containers would attract them and they would begin using buildings as shelters. Sasquatch easter egg Resources;
You'd need to make your own pine pitch glue You would need to pick up a bow/crossbow, along with learn how to make arrows (the walking dead doesn't portray them well, you WON'T be getting those arrows back intact very often, especially crafted ones)  You will end up using lower end renewable weapons that are able to shoot ball bearings like wrist brace slingshots, atlatls, hardwood longbows.  Some items would simply never run out, like plastic, or ball bearings, or sheet metal, or possibly ammunition. There are trillions of rounds in existence in the US. There are many plants and handloading tools. There are many places to source powder, and one person could never possibly use it all. You could expect to have to travel a long way to a very densely zombified area to get access to it though.  TL;DR, a zombie apocalypse would never be a never ending horde of World War Z zombies long term. It would also be a zombie aftermath apocalypse where you have to deal with thousands and thousands of rotting corpses poisoning air. You would have to deal with animals that you would otherwise eat stealing your supplies and feasting on zombies and become inedible/unusable for bait. Zombies that don't die would be too scary to want to take on with melee weapons because they learn to grab, block, or they grow tumorous scar tissue that works like armor. 
 
 
 

Endgame can kinda only be accomplished in a handful of ways, e.g.:
An actual ending (turn the game off, you beat it, roll credits). An extreme variety of existing optional gameplay mechanics that let you build and solve your own problems (maybe NPC factions would cover this) A brand new set of gameplay mechanics (some people have suggested mutations, this would fall under this, but this will still get repetitive over time and is developmentally costly. Terraria achieves it's endgame this way, effectively trying to make you sick of playing it because there is just so much content) A wide variety of collectables that in order to get all of them would take hundreds of hours to complete, and once collected give you little perks/buffs/bragging rights/ skins (this is how multiplayer games achieve longevity)
Number 4 I think is the best option for the devs and this type of game. Collectables like the Spiffo Suit. Rare weapon attachments (like suppressors, maybe divided by weapon type). Possibly pieces of experimental military tech found in outposts (like night vision or thermal optics, or a shotgun/ shotgun suppressor). Rare albino animals that give special pelts and trophy heads. A very rich person's RV lol. You get the idea, things that most people through an average playthrough are unlikely to ever encounter.
 
Number 2 could include things like plant genetics and animal taming (Rust recently added this and it's added a lot of depth for some players). It also includes things like extremely complex and rewarding crafting recipes, in addition to new content like new metal building structures and such.

I know it's a dead subject because I know it's been discussed ad nausea and understand that it's in the works, etc., but any stagnancy one experiences after being alive for as long as we're thinking is where NPCs would be beneficial. Even just generic NPCs or even just animals you can hunt. From what I remember reading, I think that's the next big thing expected to be worked on. Fingers crossed.
 
But yeah, otherwise, the goal is to simply see how long you can stay alive. I think that's always been the overall endgame. But if you try to liken this game to what one might experience in a situation like this zombie apocalypse, you'd be looking at a world where you'd see an entire collapse of government and social structures... So in an ideal scenario, once the zombies begin to show signs of extreme atrophy and die-or-kill-off, you'd likely begin to see the things we watched in "The Walking Dead" where marauders and various factions of social groups begin to move in to establish their own territories or raid existing people and factions to further secure their own holdings. I think that's probably the world that existed before humanity began to evolve into some semblance of civilized society, so I think you'd expect the same only in regression. These scenarios would pose more difficulty as you'd be combating and competing against a more intelligence opposition, but it would be great to see if this might come up when the game development one day gets to that kind of development. It'd probably be very difficult to add but if it could be done, it'd be awesome.

Late game wise I guess I'm hoping NPCs,   and keeping idiots alive,   will create some of that late game content.        Though some optional zombie twist would be welcome.   Either mutating or turning buildings into "nests" over time which would make areas more dangerous in some way.  (SOD).        Anything that adds to the danger over time would be welcome.

I wrote a similar post a while ago. No proposed solution, just some discussion in case you're interested in what was said then.

I'm trying to pick up a car key, but it just doesn’t respond, an error also comes out
https://drive.google.com/open?id=1KBwZB35aFX-eSAtXZKE0WJ5rAXy_XjV_ (Link to video)

I think many already about the need to fix the weapon, but I still did not see the answer of the developer about whether they know about this problem and whether they will fix it. There is no word about this in the news posts, and it seems to me that this does not go beyond the discussion of the players themselves. If you combine all the requirements, you get something like this :
 
1) accuracy. It doesn’t even immediately hit (With a police officer perk).
2) Ammunition weight. Huge, 100 grams in a game versus 4 in reality.
3) Speed recharge. With the same policeman perk, he barely reloads his weapon, as if he lacks the strength to insert ammo.
 
I just want the developers to highlight either :
-"yes, we know about this problem" or
-"no, we did not know about this problem" or
-"no, we will not fix it"
(This is overloading my old post because I created it in the wrong category.)

I had the same issue.
 
The car key was for Dash Elite, but the only Dash Elite close by was a burned car wreck.
 
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