I know. NPCs are planned, let's hope it doesn't take too much longer as it's been mentioned for ages as I can see. However, the game needs more "endgame content".
Suggestion:
Add quests, variable or static, for the survivor to seek out and save people located in areas across the map from zombies within a certain timeframe. Maybe they need food, or maybe they need the zombies killed nearby them. I figure you could learn of these NPC survivors from the radio or from found annotated maps, or maybe by following a trail of human activity.
The gameplay loop gets a bit stale after a few weeks of survival and this would give players something to do and seek out later in the game, other than tending to crops and doing gas runs.
PS: Some people need a "you win" screen to feel good. Could give players a rescue cut-screen after X amount of days survived while the rest of us can skip and continue surviving.