There are only three matches all but confirmed for WrestleMania 25 and that is Triple H vs. Randy Orton for the WWE Championship, Jeff Hardy vs. Matt Hardy, and Shawn Michaels vs. The Undertaker (which will be set up by JBL vs. Michaels on RAW next week).
Though Mickie Rourke is going around telling people that he won't be attending WrestleMania 25, WWE is expecting him to change his mind after the Academy Awards on Sunday. If that isn't the case, WWE is setting up a possible match where Chris Jericho will face a number of legends that he's confronted up until the 'Mania PPV, including some possible surprise legends. This would lead to a likely match between Jericho and Hogan if Rourke doesn't come through after Sunday night. It's basically a wait and see game right now.
If Rourke did come through to face Jericho, that would free up Hogan to then wrestle someone like John Cena. Cena is currently involved in a program with Edge which COULD lead them right into 'Mania. It all really depends on Rourke and what he chooses to do AFTER Sunday's Oscars. He doesn't want to risk not getting an Oscar due to taking part in a WWE angle.
Also, expect the annual tradition of Money in the Bank matches at WrestleMania to continue this year.