The big question is whether George Bush wants to go down in history as the one who did not stop Iran. There is a window for him to do something, that Obama will not want to do. My best case scenario prediction is that Bush says that he wants to hit Iran before he leaves office and that he will give Obama plausible deniability.
Obama may agree to something like this because he can always blame reprecussions on his predessor, and will have the relief of not having to make that call himself. Win/win for Obama.