Blizzard's community manager, Zarhym annouced that a new Cataclysm launcher will be added which will reduce the time you spend on downloading and installing patches.

“The new Cataclysm Launcher allows you to stream game data while you play. This will reduce the time you spend downloading, installing, and patching World of Warcraft. We will be releasing this new Launcher into the Cataclysm beta soon, and we’d like to get your feedback on the toolset and gameplay experience.” - Zarhym


Links
forums.worldofwarcraft.com - Source