The Rock is cofirmed involved and has started a rivalry and promised some action. This itself is awesome.
Undertaker returns at Elimination Chamber, although I don't know his role. No doubt the legend defends his streak at Wrestlemania.
Stone Cold is working on Tough Enough and with the WWE. They could perhaps persuade him to have some sort of role at Wrestlemania, or maybe the event persuades him itself. We were all dissappointed with no stunners when he was guest host, perhaps that would change now.
Triple H is almost guarenteed. He origionally wanted to return before, but I see no place for him at E.C. His movie is done and out so no doubt he will return at WM or before.
Mick Foley is rumored to be leaving TNA, and has had one TV role in 4 months. His good friend Rock is back, and he remains on brilliant terms with WWE, as seen when they promoted his most recient book. I'm sure he could be hevaily tempted to join aswell, and what better place than WM? Long shot though.
With 3 definite massive legenary returns, one which has a good chance and another long shot, this wrestlemania could easily be the best ever, and I mean the shit inbetween Alberto Vs Ray Mysterio and Miz Vs John Morrison, which I'm pretty positive will be the match ups.