I was actually thinking about this on my break this morning. It occurred to me that they may simplify gen 7. I even went as far as thinking whether they may make a direct prequel to Red/Blue/Green. Not sure how keen people would be on the idea of controlling a young Proffesor Oak in his early journey, possibly even in another region (can't remember if he was born in Kanto but I imagine so).
Lots of ideas. The most ambitious, I think, would be setting a region in Tohoku based around the recent environmental calamity—if they can do B/W, they can definitely tackle what would happen if a Legendary caused widespread damage or if an evil team actually did succeed at whatever they set out to do. If the main-game's going to be as easy as it is in X/Y from now on, then they need to add incentive for me to play beyond breeding and getting in on the metagame.
But even with a totally new protagonist, I could see them making a direct prequel. That would be one way to limit the amount of Pokemon in the game if that's a route they decide to take (bad pun?) and it could also be cool to see and use earlier types of Pokeballs/prototypes.
This is a great idea, and sequels would be just as fitting. There's not enough world-building for the early history of the Pokémon world as we know it, so pitting Kurt and apricots against Silph would be fascinating.
While we are at it, I wonder how a "sim Pokemon" would work out lol. Get to create and manage your own region, design towns and the layouts, choose the gym leaders and the types each gym uses as well as the level range, create caves and terrain for trainers to traverse, etc, etc.
Managing a gym would be a great post-game diversion. Coupled with StreetPass, SpotPass, and general online functions, it could act as a recurrent Secret Base in future mainline games.