I've got to say, after doing a little bit more research and thinking... I'm starting to gain confidence in my Red/Blue remake prediction.
RESHIRAM5's right in that they're not strictly done telling the XY story... but that doesn't mean that the Red/Blue remakes couldn't serve as the end to what he describes as a trilogy. After all, ORAS served as the middle chapter despite being remakes. Plus, as per ORAS, we're effectively in an alternate timeline here in Gen VI with its Mega Evolutions. So I see no reason why they'd let the opportunity to visit another region within this alternate timeline go to waste by returning to Kalos.
And aside from taking care of the Gen VI continuation side of the arguments, I'm beginning to think that the possibility of ORAS being followed up with a wholly new, non-remake, non-Z game is pretty unlikely. IMO Game Freak probably realized that starting two distinctly separate generations of Pokemon games on a single console (i.e. having Gen IV and Gen V both on the DS) is a little bit weird, so I think we'll be riding the Gen VI train all the way until the 3DS gets a successor.
Based on hints I've seen in ORAS, I'm pretty confident that both a return to Kanto and a return to Sinnoh are in the pipeline. So lastly, why I think Kanto's dropping first is simple: Diamond and Pearl are still playable on the 3DS, which means they're not as high of a priority. The 3DS successor will likely retain 3DS backwards compatibility, but it may lose compatibility with original DS software. So basically, Gen IV remakes can wait until they can use the excuse of necessity. Whereas they've already got that excuse available to be used to justify Red/Blue remakes, in addition to the fact that it's Pokemon's 20th anniversary. But of course, there's also the fact that the hint at a return to Kanto is delivered in exactly the same way that XY delivered their hint at a return to Hoenn: A backpacker.
And although this is far too simplistic to be considered smoking gun evidence, here's one final nudge for those who want to believe but aren't yet convinced: What colors are X and Y? Red and blue. What colors are ORAS? Red and blue. What colors will the final entries of this generation be? Hmm...
However, I still have some doubts... I don't think we have all the puzzle pieces to be able to put together a clear picture of what the next games are going to be. I think Kanto's likely to be a piece of that puzzle, but there's clearly more to it than that.