Well, since we've gone around the island and to the center (or at least what we think is the center) of the island. Maybe the next one will bring together the various communities somehow?

Of course though, Isola is probably bigger than it seems like, so there are plenty of unexplored areas inland. Or perhaps, underground, caves have been involved in the storyline a few times. Mostly in getting people to one area of the island or another, but the fact that the intro to VV4 says that the expedition took several days lends to the idea that the island is much bigger than we think. So theres plenty of places, like maybe that huge central valley we always see.