I can definitely hope for Stinger. But realistically I just cant see it. Unless the money offer was huge. Personally id much rather see guys who have sculpted mania to be in attendance. Austin, Rock and even Hogan.
As for Golberg, no thanks. WMXX was enough to put me off him appearing at Wrestlemania ever again.
The Cena heel turn/streak ending talk has been done to death, but I really think the WWE would be missing a MASSIVE trick in not doing it.
The way I could see it happening, not that it ever will, but still:
The WWE title match is the second last match on the bill. Triple H goes into the match as the self-crowned, super heel champion. Bryan overcomes him in an epic match leaving Trips embarrassed and raging.
Streak vs. Career is the main event. Epically long match ensues, Taker has it won, then Triple H interferes, KO's Undertaker and Cena pins him, ending the streak, keeping his career intact and becoming a mega heel. /end PPV
As I say, almost definitely won't be how it goes down, but I think it could be perfect. The WWE gets a proper new face of the company in Daniel Bryan, and Cena turning heel and aligning himself with Triple H could lead to an amazing Bryan/Cena feud following WM.