Goldberg says he left WWE because of the way the company was being run, and he only came to WWE because of the fans. He was not concerned with money when shifting companies...
Stone Cold, he is still under contract with WWE with Touch Enough, and he said in a recent interview about coming back to the ring for more hands on approach.
Sting, eventhough he says in an interview, that Vince begged him to come to WWe, he saw the way WCW stars were treated when the flocked over and decided not to go. However, Sting's contract is almost up, and you never know!
Kurt Angle, same story as Sting as far as the contract, but, Kurt would be a good opponent for Taker.
Brock Lesnar, it was rumors that Vince and the owner Dana of UFC were in talking about letting Brock come back for a one time match seeing how Taker and Brock got into an argument at a UFC event. Who knows..
HBK, come on now...
HHH, I foresee Taker stalking him until he decided to fight him...