This was likely a tease for the Dead Man's return to work a match at WrestleMania, much like has been done with Shawn Michaels a couple of years ago.
We reported the following on December 6th, 2012:
We can confirm that The Undertaker reached out to WWE during the past week or so and has told the company that he wants to work the WrestleMania 29 pay-per-view. He is currently training for a return and pitched a potential opponent for the event. At this time, it is known that the possible opponent will NOT be Triple H or Ryback. Of course, plans can change.
For those unaware, 'Taker has a gym and full-sized wrestling ring at his home he shares with his wife Michelle McCool.