They're already in the BW2 events for the Japanese anime (he beat the Poison type Gym Leader and is now in the World Tournament for example) and Ash is still there.
There might be a few episodes without Ash eventually, like with the Brock episodes at the end of Gen IV series.
And they might make another series like Pokemon Chronicles to show us what is going on with all the characters we met in the other four generations worth of anime.
But there is no word of this, so I find it unlikely that this will happen anytime soon. For news on the anime, use serebii. http://serebii.net/index2.shtml