Ash had many pokemon in Unova and he held them in rotation. The screen time was not fair shared but it was fun that teh writers tried this. Now do you think it is time to let Ash rotate all pokemon he has in his team together with his Kalos pokemon. They already started with this when they let Charizard back. But in such case the writers would have to make the Kalos series bigger than before to get room for screen time and development to everyone. How could they do this and do you want them to do this?