Do you think there will ever be a game featuring a World Champion, a Pokemon trainer that's defeated all the E4s and all other champions in order to become a true Pokemon Master? If so, do you think it'd be any existing character that would claim the title (such as Red) or would it be someone new? And what do you think their party would consist of?
For consistency's sake, let's assume their party is averaging in the 80s with a level 90 for their signature Pokemon, and limit any legendaries/pseudos to one only (this IS someone who's basically beaten the best of the best around the world, after all, but a level 100/party full of legendaries might be too difficult).

The only way I could see this happening is if a Pokemon game revolved around traveling the various regions or featured all the other champions within one huge region, perhaps as some sort of Ultra-League. Maybe you'd have to face off against all the other champions before fighting the World Champion, as a sort of super E4.