There is no way Charlotte does this for the following reasons:
1. They really like MKG and do see All-Star potential. He is only 19 and already an average offensive player with room for improvement, and will certainly be an elite defender.
2. Rondo has two years left on his contract and probably would be out of there in a heartbeat, probably to the Lakers or some nonsense just to spite Danny.
3. Even if they don't see MKG as a franchise player, they are going to have at least two more shots at the lottery in the next two years with him on the team, and then it would take 2-3 years for any franchise player they get to develop. By then Rondo is maybe 30 or 31 (or gone!), while MKG is still only 23 and just hitting his peak.
4. Walker has shown close to Ben Gordon-type offensive numbers while being a much better defender. He is a valuable piece in his own right.
5. Rondo has proven to be a great player when surrounded by other great players, but hasn't proved that he can play well surrounded by a weak team. I'm not saying I think he couldn't do that, but for any offensively limited player that is going to be a concern.