If my past experience means anything, the last two Bungie games were both released in September. They both had betas, which lasted throughout the month of may. I'm gonna go out on a limb and assume they're following the format they know best, and will launch the beta this late April at the earliest, but probably early May. Hopefully Bungie does some kind of Friends and Family early release again, because I managed to get in early in both the Reach and H3 betas that way. :D