What is the release date of World of Warcraft: Cataclysm?

The latest rumors place the release date for World of Warcraft: Cataclysm indicate that the highly-anticipated expansion pack will be released in 2010. WoW has become the most popular MMORPG by a significant margin, and the previous expansion pack to the game, "Wrath of the Lich King" was released in November, 2009; given that the next expansion is so highly anticipated it is quite possible it will be released later in the year, however the release has not yet been announced.

WoW: Cataclysm Release Date -- what is it?!