Next Raid Encounter will probably the Ruby Sanctum
There is a nice interview of Tom Chilton (Kalgan) on Gameinformer.com. We learn a couple of new things here, including an almost-confirmed upcoming single-boss raid encounter: The Ruby Sanctum in the Chamber of Aspects under the Wyrmrest Temple.

  • The Dungeon Finder tool might be extended "at the very least" to 10-person raids at some point in the future.
  • The next addition to raid content will probably be a single-boss encounter in the Ruby Sanctum of the Chamber of Aspects. "It’s a little too early to have a lot of details on that, but I wouldn’t characterize it as a huge chunk of content. [...] I think of it more as an extension of patch 3.3."

They are the two major announcements of the interview, I suggest that you read the full article on GameInformer.com if you want to read the rest, there are a couple of interesting commentaries about Wrath of the Lich King's development after the original release and how it will affect Cataclysm.

Fonte