I kinda wish that GameFreak would throw us another curveball with the next generation. Get everyone thinking that we're gonna end up with Gen 4 remakes, but instead they surprise us with a Kanto/Johto based SEQUEL. It wouldn't have any new pokemon (barring what we get next gen) but it would take place in a Kanto/Johto that's current with the latest game in the timeline.
Saffron/Goldenrod/Celadon have expanded into full-fledged cities ala Lumiose with Celadon being full of shiny, reflective buildings and plants growing everywhere, Saffron being a high-tech metropolis, Goldenrod having some kind of hollywood feel to it with media studios everywhere. Lavender town could be much more eastern-styled, Blackthorne could have a more tribal-feel as a mountain dragon village, etc. etc.
Basically beef up the flavor of all the towns and make Kanto/Johto feel like it's grown. Shuffle around some gym leaders again if neded, change what cities have gyms, give it a new and fresh feel so people can revisit the place it all began, but experience a brand new adventure. I think it could be easily done if they wanted to, and not in a way that panders to genwunners.
