Irvine-based Blizzard Entertainment said that its third expansion for World of Warcraft is expected to debut in stores on December 7th. The firm--which has been running a invite-only beta of the expansion pack for World of Warcraft since July--said it will make the release available for Windows XP, Windows Vista, Windows 7, and Macintosh computers both at retail stores and online as a download. Blizzard said Cataclysm includes "the best content we've ever created for World of Warcraft."