This is a tough one to call but I think we can say for certain that Chris Jericho v Edge will not be the show closer, which is a pity because of the whole "the winner of the Royal Rumble main events Wrestlemania" but last year was the first time this had happened since WM 21 so it's not that big of a deal any more. Plus the build up to Jericho / Edge has been weak and doesn't befit the status of the most important match on the biggest card of the year.
As for the other three matches they could all theoretically close out the show.
Bret Hart v Vince McMahon is a huge match, given their history, but you'd have to hazard a guess that from a match quality standpoint this won't be the best. Therefore you can't close out the Grandaddy of 'em All with a potential dud - although the pop will be awesome when Bret turns Vince into the Sharpshooter. This one won't headline on Sunday.
Now comes the tricky part. Undertaker v Shawn Michaels is a huge match, the biggest on the card even though there is no title at stake. However, the problem with this match is that whatever the outcome, a large number of fans are going to be disappointed. Whether you end the streak or HBK's career there will be a lot of fans in attendance that are pissed off, so for that reason I can't see this being the show closer either. If Shawn loses he can do the big goodbye on RAW if need be.
So for me the main event of Wrestlemania will be Batista v John Cena for the WWE Championship. The build up has been great, Big Dave's been an absolute revelation and it will send everyone home happy when Cena vanquishes the big, bad bully. At least, that's the way WWE will rationalise it, I'm sure there are plenty of people (myself included) who'd prefer it if Batista retained the title.
