At this point, it looks like there will be a ton more choice as far as viable classes/specs go. Pretty much anything will work.
My opinion? Druid or shammy. A warlock may very welll be mandatory on every self-respecting team for health buff (priests apparently get at 22 now) and UA since rshaman and potentially other healer specs will get dispels by 19. Currently rshaman gets at 18 (woot), rdruid gets at 22 or so. If you run premades and your group doesn't have a good warlock, that could be a good choice. Balance/Feral druid looks very strong for solo play.