It's July 27, 2010.
Alerted by: Chak
Press release: http://eu.blizzard.com/en-gb/company/press/pressreleases.html?100503
PARIS, France – May 3, 2010 - Blizzard Entertainment, Inc. announced today that its highly anticipated real-time strategy game, StarCraft® II: Wings of Liberty™, will arrive in stores throughout the United States, Canada, Europe, South Korea, Australia, New Zealand, Russia, Mexico, Singapore, Indonesia, Malaysia, Thailand, the Philippines, and the regions of Taiwan, Hong Kong, and Macau starting on July 27, 2010. Players in several of these regions will also be able to download StarCraft II: Wings of Liberty and activate it by purchasing either the retail package or an activation key from Blizzard Entertainment shortly after the retail launch.
Official site: http://kr.starcraft2.com/splash-launch7.xml
Alternative site: http://multiplayerblog.mtv.com/2010/05/03/starcraft-2-release-date-confirmed/