http://us.battle.net/wow/en/blog/11275287
Beginning today, October 15, players are able to get the original World of Warcraft, The Burning Crusade, Wrath of the Lich King, and Cataclysm for only $19.99 as part of the newly upgraded World of Warcraft package (formerly known as the Battle Chest).
In addition, all World of Warcraft subscribers now automatically have access to all of the content and features of these expansions at no additional cost.