It is most likely we will have split servers in the sense that there will be multiple NA servers, multiple EU servers etc. depending on numbers but they will not be region locked, you can play on any server you like, you just may have to put up with some ping issues and lag if you join one far from your location. We won't have mega servers like some newer games as we believe less (or none if possible) instancing and capped server numbers is a better approach to a game like Pantheon.