Unfortunately I don't think Diablo III will be released in Q2. Why? Blizzard has not even announced a single detail about the new skill and runestone system. This is the biggest and most complex aspect in Diablo III. Once they do, it will hit beta servers in about a week. After that the beta testing will begin, there will be LOADS of feedback. This feedback will make sure there will be at least 6 more beta patches with 'endless' iterations. The same thing happened when they launched the beta. "Just for infrastructure". Almost 6 months and 12 beta patches later there is still no sign of a release or even a rune system.
I really, really hope I'm wrong. What do you think?