Just fooling around with a bit of math here - 1920 x 1080 = 2,073,600 pixels.
At 30 FPS thats 62,208,000 AA algorithm passes every second
I've seen posted performance figures of 196,317,394,651 operations per second(!) for the GTX580. To put it another way, just under 200 gigaflops (I kid you not)
So assuming the AA algorithm involves less than 3155 operations we should be OK.
Before anyone comments I appreciate that the graphics cards do a lot of things over and above AA calculations but it was an interesting experiment.
Jabo