He's also not going to be using his old Pokemon in the Sinnoh League, because in the beginning of the Sinnoh & Hoenn arc he said that he's only going to be using the Pokemon he caught in that region to use throughout the Gyms & League.
Well, the preview for next weeks episode show him using Quilava and Heracross in the league, so that's kind've debunked.
And yes, he released them. They are not under his care anymore, they are under Liza's and Officer Jenny's. However, they still have loyalty to ash, as he still does own their pokeball. He still owns Butterfrees, Pidgeots, etc though too. He released them. It doesn't mean he got rid of them.