I have the theory that, more or less, the Pokémon verse, being an altarnate version of our world, follows real time dates, which would mean that probably it's been around 17 years since the original Kanto events), so I want (I need!) to know what was happened to the region in all these time. Is Red still the strongest there (PWT in B2W2 implies that indeed he is)? If yes, is he still the unofficial champion with Lance being the official one? What about Blue? Is Oak still active or did he retire from old age? And so on. So, instead of disliking a Kanto sequel, I'd gladly welcome it.
Also, as Bolt said, Game Freak gave us a new Mewtwo forme, 17 years after its debut, meaning they're not unwilling to change old things.