He could opt-out of his contract (player option), something that might be advisable considering the upcoming CBA and his stellar performance once he joined the Bucks.
Although I see the Bucks doing everything in their power to get him back, any chance the Raptors could get him? I think he's a pretty good player at the spot (borderline all-star). He did reject our offer a few years back and went to Sacramento, but I hope that doesn't affect anything.
I personally would rather have him on the Raptors than Joe Johnson.