John Morrison is the person that first comes to mind although I don't know if I am reading too much into the rock comment. Then again I dont know if he would be considered a BIG free agent.
Christian hasn't been seen in WWE for quite some time even though he is apparently cleared to wrestle. Maybe he is heading back to TNA to be a top dog over there?
Hopefully TNA actually deliver a BIG name and not just some random midcarder.