If AT&T is smart, this is an LTE launch device, which means that July is likely the earliest time (LTE is rumored to hit NYC June 30th and LA in July). It would be a crime for this phone to come out and not be an LTE device.
They could actually beat Verizon to the punch with the first dual-core LTE smartphone (Droid Bionic will be Verizon's first with no clear launch date yet).
And for God's sake, put a decent battery in this one HTC. AT LEAST 1500 mAh, preferably 1700 or better.