In an interview last week Blizzard said Starcraft 2 will definitely not be launched this year:
Speaking of secrets, what is your timeline for release for “StarCraft II?”
It’s a secret! I can give you the old Blizzard mantra of: “It’ll ship when it’s ready,” but it’s something that historically, we’ve learned to keep release dates really close to the vest. I think all game developers are extremely optimistic, and we used to give optimistic dates and we’d disappoint our fans when we didn’t hit them. So now, I think we’ve just gotten more gun shy. The only thing I can give you [that’s] concrete is it’s not going to be this year. Some people were hoping, because of how advanced the game looks, that we’d have it out by Christmas, but that’s definitely not happening.
Blizzard also said in the interview that they began working on Starcraft 2 in 2003.