CHIME NOISES INTENSIFY
I honestly doubt there will be travel between regions. Pokemon is a company after all, and remakes as well as new games would bring in more sales than just one set of games. I could potentially see you briefly visiting a region, but only very very briefly. Would be pretty cool though! Actually, what I could realistically see them doing is having a cut scene where you're flying OVER another region, so you get an aerial view of it, but you never touch down on it. Or maybe there would be a scene like in Diamond/Pearl/Platinum(?) where the legendary goes crazy and you see a view of the entire region - except this time it'd be all the regions.