If Howard were willing to sign an extension with Boston, this would be a no-brainer for the Celtics. While Rondo is a great player, Howard is one of the few players that you unquestionably trade him for.
I would see if it were possible to move some first rounders instead of Bradley, though. I can't help but think Orlando would rather bottom out, though. I don't think Rondo is a guy who can lead a bunch of awful players to a title, but he is certainly a guy who can lead a bunch of awful players to an 8 seed in the East, which is not helpful in any way.