Daniel just put this perfectly in the latest MSDN newsletter. You may not think it is perfect as it doesn't tell you a whole lot but trust us! Daniel & I had to fight to even get this much info out to at this stage
Keep the 18th & 19th March free in your diaries...block it out now......cancel any family birthday celebrations or meetings!
I'm sorry I can't tell you more but I promise that it will be worth the wait!
Is it the release date for Halo 4? ;-)