Late game continues to be a really active topic of discussion internally, and there are a bunch of systems designed for this, but they're basically contingent on interactions with the parts that are at play in the early game. There's a ton of work done on buildings, machines, and monsters that we haven't discussed and aren't in the game, but we're holding onto them until we can add them later.
As an example, David and I have been talking quite a bit lately about what we've internally labeled "dynamics lines" (power lines, water pipes, etc.) and how we can make these systems work to improve the player experience without cluttering too much. Everything but the visual design i'm sold on: it frees characters to be more productive (cause more trouble) and allows players to improve rates of production of food, weapons, building materials, and stuff like that. We're running some tests to hopefully come together on the visual design as well. I mention that system because it's a "late game" ish thing. When most everyone is dead due to some mysterious illness, you need fewer people to be able to hold things together.
In general though, we'll be rolling out most of the later game stuff as we do early access: we want a stable base to grow it. Also, we don't *really* know how a large group of players is going to play the game, so we want to be able to prioritize parts of the game that people seem most interested in pushing toward. I suspect that most people are going to really want us to finish the concurrent multiplayer implementation ASAP so they can mess with each other, which will lead to people wanting more sophisticated and horrible ways to mess with each other, but we'll see