You did see the outposts in the trailer, right? The place where you had to go rest at a tent, and craft items by speaking with the shop owner there?I really want to know how exactly the regions will be gated. That's like, at the top of my list of things I want to know about this game. It makes a huge difference in how it plays.
I'm certain that you need to fulfill certain requirements to be able to expand and set up outposts (or as part of the story plot requirements). And because you need the outposts in order to explore within the outposts' designated boundaries of the regions, I guess that you will probably be blocked off with an invisible barrier notifying you not to venture out too far away from the outposts.