Yes, it’s official, and probably not a surprise to many. Blizzard has announced Starcraft 2, and it’s in the Diablo vein. A single-player game with online play via Battlenet.

They also mention scripting and mapmaking tools, so it could be that they’re allowing for mods this time. Xian posted the link in the comments to “Slow Week”, but I’ll put it here for easier use:

Starcraft 2 official site