I think the all region thing is probably not the best move Nintendo could make with this, to be honest. Sure, you could nostalgia everywhere, but there wouldn't be much to do, since most people have very high-level Pokemon by the end of the game already. Gyms would have to be like lv 100s and the E4 would have to have competitive Pokemon and AIs to make for a challenge. If they were to make online multiplayer, however, that could add a lot to having every region, though that's probably never going to happen.
I think that there's probably more to Kalos than we know about. I'm talking like secret areas or places disconnected form the main area we all know, such as underground (couldn't we do that in DPPt?), or behind the GIANT ASS MOUNTAIN RANGE SURROUNDING KALOS. Also, correct me if I'm wrong, but isn't this the only generation without a city on an island or in the water? That's kind of suspicious. Other than that, however, I have no idea. I'm hoping that backpacker guy is someone important, because two regions would be amazing and I would probably buy an extra region for this game, albeit begrudgingly.
Touching on what Requiemon said, adding in HMs seems likely, since this is the first game since Gen II that hasn't had a unique HM (Other than BW/B2W2, but they're pretty "special" themselves). Of course, I might be over thinking things, but that article got me going. Overall I'm incredibly hopeful for this game. Hell, maybe there'll be an update released with the Pokemon Bank that adds something more. Seems like something Nintendo would do.