Undertaker has been in negotiations with WWE about working Wrestlemania 29 this year. While his health is obviously a factor, the main reason he was holding out was over money.
We can confirm Undertaker met with Vince McMahon and Triple H about Wrestlemania two weeks ago in Nashville, TN. We reported on February 14th he was still a possibility for the show.
As of this writing we are unable to confirm Undertaker for Raw on Monday or that he is officially in the plans for Wrestlemania 29. He lives just over an hour and half from Waco, Texas (the site of Saturday night's live event) and it's doubtful he returned for one non-televised bout.
A source that has been following the negotiations said Undertaker wanted to test his body before a match and given the fact he worked a tag bout [at Saturday's Smackdown live event], it makes sense.