When is the World of Warcraft expansion released

Two already have been released:

Late 2007 The Burning Crusade was released with character levels possible moved to 70, new mounts, a new continent: Outland was added, and many new instances (including The Black Temple where Illidan awaits.)

Late 2008 (November) The Wrath of the Lich King was released which bumped levels possible to 80, added a class: Death Knight and new instances and new lands along with new mounts. Catyclysm has been anoounced