@Cyber, for me: Dawn's returning to the main cast > Ash's leaving the show and the anime making a robot.
Sorry, but Pikachu (and specially Ash's Pikachu is the face of the Pokemon franchise. They aren't going to ditch that status so quickly. I don't know what will happen but i don't think that Ash is going to leave like others will.
To be more precise, Ash and Pikachu appear in the Best Wishes series where older pokemon doesn't appear, old references doesn't exist, etc. If they want to make a reboot of the anime, they made Ash leave in DP191 (with making AshXDawn couple?) before BW1 starts.
The pokemon anime isn't for CyberCubed. It's from kids from 4-15 years that probably didn't known anything apart from a few episodes.
For me, if a character survived the transition from DP to BW, that character won't leave the show until the end of the show. And how knows when...