Part of me feels that even if the franchise doesn't die down anytime soon, that there will be considerably less new Pokémon additions in the future, to maybe even a point where there's a Generation that introduces no new Pokémon at all.
Think about it, after having at minimum of 100 new Pokémon per Generation, X/Y introduced only 72.
Granted, Mega Evolutions became a thing, so the new Megas are sort of like newer Pokémon, but still.
I agree with this, and want to see it happen. I've been a Pokemon fan all my life, and have played every generations game, but when people start to mention Pokemon that I don't recognize the name of? I think it's starting to get a bit ridiculous. I'm hoping for a game that takes place with no new Pokemon, no new region, but a whole new story.
In terms of the whole Fire Emblem has too many characters idea, I think it may have to do with the fact that the series has so many characters, and Sakurai has taken a liking to quite a few of them. (Similar to how Pokemon is) If Roy does become playable, I don't think Sakurai would have him like Marth and Lucina, either he'd be a "clone" like Wolf is to Fox or he will be his own original character.
Don't forget guys, this is Sakurai. He doesn't care much about popularity and by sales who deserves to be in or not. This is not only supposed to be fun for us, but for him as well, and if he ultimately doesn't want something, you can't make him do it. It's like visiting a friend's house and not following their rules. He's the creator, who cares what you think?