Why exactly is Ash still around after 15 years? They got rid of Misty a decade ago and never looked back, and Brock finally left the show last year. The original trio never saw the light of day since the end of Johto, so why not retire Ash himself and start with a new hero? Bringing in May was their first experiment with a new game hero as a main, so I don't see why they didn't do the same with Ash. You could argue Ash is marketable and well known, well you could say the same for Misty and Brock and they're long gone. I think it would be easier for the anime to start off fresh with a new cast, rather than sticking to the same continuity for 15 years.