Rumor mill is that Motorolla will drop a flagship, high-end device for ATT soon. Check out the "rumor" forum below this one.
On the other hand, Captivate and Streak are the only real choices for Android (oh, and the Aria).
It seems as if ATT wants to focus on Microsoft and WP7 as they are releasing several more WP7 phones. So, I think that is the direction they are taking ... staying away from the open-platform and looking at the two big locked-down players (Apple and MS). Which is fitting for ATT, the carrier who likes to lock-down services.
I think Android will be only a few top-shelf devices.