Nothing definite has been decided in terms of The Undertaker's status for WrestleMania 29. As reported, he wasn't backstage at RAW last week despite being in Nashville the night before, though he did reportedly did have a meeting with Vince McMahon.
In the photo that was taken at the Nashville hockey game, he appeared to be in better shape than he had been and that led to speculation that he was ready to come back. He has undergone major surgeries since last wrestling at WrestleMania 28 ten months ago.
Those close to Taker say that if he doesn't do WrestleMania this year, it means nothing in terms of his retirement and only that he didn't have enough time to recover from health issues. The belief is that he would like to return for WrestleMania 30, which could be his last hurrah.
If he is working WrestleMania 29, he will likely appear either at Elimination Chamber, or the next night on RAW.