The Starcraft II beta starting this summer is a sign of things to come. A release date is a sign of we things come to all of us. We don't have a release date.
Though, we do have Blizzard's Mike Morhaime saying that Starcraft II will be release in 2009 as long as it "meets our standards and the expectations of our players".
Blizzard has high standards and so do Starcraft players. We hope they're able to see eye-to-eye this year. If not, hey, we'll wait. Better late than rushed.
E3: Morhaime: Starcraft II probably in 09 [Eurogamer]