Check that out. Why would they go through the trouble of making an SCII trailer without actually starting on the game. I think they're definetly going to make some kind of SCII, whether it's strat or mmo. We'll just have to sit and find out.
They haven't released much info about it, but there's evidence that they may charge to play this over Battle.net.
IGN Article said:
Blizzard was silent on whether using Battle.net for StarCraft 2 would require a charge or subscription fee. The service will certainly have new features, Blizzard assured the press in the audience, but they weren't willing to get into pricing specifics.