Kramnik
Who do you hope will challenge carlsen next year?

Kramnik. Although if Kramnik plays, the match may get very boring when Carlsen plays the white opening, Ruy Lopez... Kramnik's Berlin Wall even held off Kasparov...

Aronian, he is #2 and i think maybe better than Kramnik
(actually i think it will be Houdini)
although Vesilan toplav has a good chance.

From the list, Aronian or Kramnik would be nice. But I would very much like to see Anand retire from World Championship chess and focus on his tournament play and stay on top for at least 5 more years. It will also be very interesting to see Caruana win the candidates as a wildcard and challenge Magnus!
Peter Svidler is the wild card.
List of candidates:
Loser of World Chess Championship 2013-
Viswanathan Anand
The top two finishers in the Chess World Cup 2013-
Vladimir Kramnik
Dmitry Andreikin
The top two finishers in the Grand Prix 2012-13 -
Veselin Topalov
Shakhriyar Mamedyarov
The next two highest rated players who played in the Chess World Cup 2013 or the Grand Prix 2012-13-
Levon Aronian
Sergey Karjakin
Organizing commitee's wild card (FIDE rating in July 2013 at least 2725)-
Peter Svidler
So which one do you root for next year?