Who would I like to see winning it off him? Good one.
Firstly, I'd like to see Punk retaining the title through Wrestlemania season. Imagine that. That would see him amass a 450 ish day title run. Something we won't see again for a very long while yet no doubt.
Eventually, I think Punk is going to turn face again at some point in 2013. I picture it that Heyman and Punk will have some argument or their alliance will become strained. This will lead to Heyman bringing in Brock Lesnar who will cost Punk the title, turning Punk face, and they'll go on to feud.
Question is, who would he drop it to.
I'd say a rebuilt Miz could be a good choice. Miz is on his way back to the top or so they say, and I wouldn't mind seeing him given a run as WWE Champ again, this time as a face. If Chris Jericho returns, I hope that he comes back for one last full time run, and is given another world title run. It could be cool to see a face Jericho winning the title off Punk. Others I wouldn't mind seeing winning it off him would be Ziggler or Barrett.