I hate how they make him a total idiot each time a new saga starts, and occasionally during that saga as well. It's becoming old, and very annoying, especially for people who have been watching the series from the very beginning.
IMO, he should at least be rebooted along with the whole anime series. After seeing that anime trailer for B2W2 a long time ago, that made what we have now seem like crud. If the anime was rebooted in the style and awesomeness of that anime trailer, I'll hug all the people behind it. Have Ash actually age, showing how mature he's gotten and how better of a battler and trainer he's become. Change up the formula too, as every saga is as predictable as what a wild Abra will do:
Ash will go to a new region,
lose to the jerk rival,
get badges between fillers,
meet other people who he will take on the League with,
meet the nice rival,
beat the jerk rival in the League,
and lose to the nice rival, who may or may not win the League.
So, no, don't replace him as he's practically the face of the series, but reboot the series and Ash as well.