I am not sure that JR has anything left. Waiters does, but I think he is a terrible stylistic fit for this crew. And, inside the bubble, his timing has looked completely off (which is understandable considering he did not play much of any this year).
The guy that they need to take a step forward, in my view, is Caldwell-Pope. He fits everything that they need that player to be (take care of the ball, hit open shots and play D) and has largely done the role well this year. But, he has to hit shots. He has the ability to hit them and he gets very good shots just from playing with LeBron and AD (like everyone else on that team).
I also think that getting back Rondo will not hurt because he makes the game easier for everyone and allows James to take a break. He will be back this series at some point, it appears.