think I'll re-write this post because Gen 6 is actually a bit older now that I originally though (3 years seems a pretty standard duration) but I'm still hoping it's not Gen 7 because there are still way too many loose ends in 6 (like, ALL of the legendaries, AZ's floette, and pretty much the rest of the complete works of Shakespeare found in the X/Y game files).
"sun" and "moon" trademarks apparently got registered earlier by Nintendo in Europe (can be looked up
here) which I guess is something but does nothing to help the "Game Freak is running out of names" idea. Can think of a lot of possible extra evolutions/mega evolutions that might come with that, though, so I guess Sun and Moon for Gen 7 wouldn't be the
end of the world. Probably would be mythology themed or something.