>>39184000There's no such thing as an "end" for Ash and the Team Rocket Trio until the heat death of the universe forces an end.
Ash is considered a timeless icon like Mickey Mouse, he's too recognizable to replace, especially given the Pikachu-shaped Tumor that ensures that even if he were replaced, his replacement would just be a carbon copy who also has a Pikachu-shaped Tumor, to which case it begs the question "why even replace him if the new guy's more or less the same thing?"