On July 16th Blizzard noted that they are having three teams working for three different game projects. Frank Pearce from Blizzard informed that the latest will be something "totally awesome".
Now, some of the speculations can be flushed off the toilet, when The Inquirer succeed in stalking Blizzard's employees at Austin GDC last week. Project's codename is Hydra, but according to a former Blizzard employee, its only a hint that needs to be solved. See this forum post.
This was what The Inquirer's staff heard:
Blizzard Employee 1: What are you working on?
Blizzard Employee 2: Starcraft II, and you?
Blizzard Employee 1: I am working on Hydra.
So, with this news stay tuned here at SK Gaming for further news regarding this game project!