Dawn's probably going to leave. There's nothing for her in Johto. The contests are gone. I'd like them to bring Misty back, but I doubt that will happen. I actually don't know what's going to happen. They'll probably do a small promo on Johto, but not travel the entire region again. They'll possibly meet up with May for a while. Anyway, Brock's probably going to stay through that as well as Generation V. Then, they'll almost definately get another new character. Considering Dawn won't have much of a purpose, I'd say she'll be the one to go. It's possible that contests will be completely left out of the next generation. Brock, on the other hand, is a Breeder, so basically he can just do anything. He was always just there.