A Q2 2012 release is what it was on the April 2010 product schedule that was leaked and I suppose a that's not too far off. However, that same schedule had Diablo 3 and the SC2 expansion (Heart of the Swarm) as a Q4 2011 release. While Diablo 3 finally has a release date (6 months late), the SC2 expansion does not.

Having a beta in March is promising - WotLK beta invites went out around July 11th (2008) and Cataclysm beta invites went out on June 30th (2010). Unless they are farther along than usual, maybe we can expect a release in August?