Maybe. In the latest issue of New In Chess Magazine, there's an interview with Viswanathan Anand shortly after his lost match to Magnus Carlsen. There he tells the interviewer, Dirk Jan ten Geuzendam, that he intends to play in the upcoming Candidates tournament in March of 2014. Dirk Jan seemed rather unconvinced by this, and now he seems to be leaning against playing (HT: Brian Karen).
If he still has any aspirations to compete again for the world championship, skipping out on this seems like a big mistake. For one thing, qualifying for subsequent Candidates events from scratch is not going to be easy, so he should take the free pass while it's there. Second, he must still have a nice bank of theoretical work from the match that will still be usable. In time it will seep out in tournament and others will catch up, so he should use them while he can.
Suppose then that he does drop out. Apparently Fabiano Caruana (send him back! [or now that he's 21, come home!]) is slated to take his place. I don't know if that's true, but he would be a very reasonable choice. Whatever the case, I hope Anand makes up his mind soon, as this would be an incredible opportunity for Caruana or whoever the replacement is, and they should have as much time as possible to gather a team and prepare.