I suspect that this announcement will be something regarding starcraft or a diablo MMO. But, truth be told, I'm not really happy with Blizzard right now.
World of Warcraft was my drug of choice for a good long while, but it got very frustrating towards the end. Aside from the infighting in my guild, the drop rates for gear as well as the vast imbalance between a few classes in PvP and PvE, I've lost faith in Blizzard. I don't think they can make good dames like Diablo, Diablo II and Starcraft again, I think that they're entirely too happy to suckle at the MMO money teat.
I don't blame them, however. They're in this business to make money, but as of this moment, approximately 5 months away from 2007, I am just not excited about their announcement of an upcoming announcement.