The following is courtesy of PWInsider.com
It has been discussed of having The Undertaker compete at the 2013 Royal Rumble, possibly as a surprise entrant. They have left the idea up to him when to return, and if he wanted to have a lengthy storyline and build to Wrestlemania 29. While many people have discussed who his opponent will be, there is still feeling in the company that Undertaker may not want to have a huge match and build like previous years.
Even though The Rock will compete in the WWE Championship Match at the Royal Rumble, WWE officials still view this as a top three Pay Per View, and would love to capitalize on the buzz surrounding the event.