Pokemon Black 2 and Pokemon White 2 will feature new characters and maps. In the beginning you'll be able to chose to play as a male or female trainer, both of which are brand new! Naturally, your rival will be a new character as well. Akuroma has been announced as the "Pokemon Expert," but it's not clear if he will serve as Prof. Oak or Bill.
Two gym leaders have been revealed as well. Their names are Homika and Shizui. I think it's safe to say their name will be changed when the game is released in America.
Pokemon Black and White 2 will begin in different cities than the first game in the Black/White series. It will be released in Japan this June. An American release date has not been announced.