They may be one company (I knew that !) but you don't see Activision rushing the release of Diablo III now do you? They've even announced a console version so that means another 1-2 years before we get a release date (Imo). So I still trust Blizzard
That's why I'm cuddling my theory of Blizzard retaining a controlling stake in their property.
I believe D3 is scheduled to come out towards the end of this year sometime.