So I'm watching the replay. It's a weird play, I don't see any awkwardness to the play. Here is a replay(and a plug for a nice video)
http://www.youtube.com/watch?v=f4J9IwYt ... ded#at=148BG dunks the ball at 2:21, You can clearly see him grab his left leg, but BG doesn't even land on it hard

.
Upon watching the game on my DVR, BG continues to play the 3rd quater out with no obvious limitations.
I say he will be available on opening night. He may come off the bench.