It's a direct sequel. RTS in 3D. New units, old units, and updates. Multiplayer using all three races out of the box, but the only single player campaign is the Terrans. SP modes for Protoss and Zerg will be released later.
Yeah the FPS was cancelled a few years back, I think Blizzard decided to pump more effort into woW, considering it makes them a little bit of cash every now and then...
The Terran story mode is brilliant, really well designed.