It seems like it could be anyone at this point honestly.
What seems somewhat likely but still unexpected is Orton becoming a sympathetic face as he is 'fired' and HHH takes the title for his (official) last championship reign.
However I don't really think HHH is that much of a dick to position himself over others when he's a part timer - so I'll probably say that Orton will lose the title to Punk.
Only because Punk hasn't been involved in the title picture for almost ten months(-ish) and by the time this Wyatt feud is properly over I imagine the Rumble will come around; and if Punk doesn't win the 2014 Rumble I expect him to win the title.
...But then again I think Punk has a huge chance of winning the Rumble in 2014 (unfortunately - I'd rather see a younger guy win...)
So yea, like I said, it seems to be really difficult to say at this point.