Before 2016? That'd be interesting considering he's got most of this year preparing for his UFC debut. Punk strikes me as a Bruno/Hellwig/Hart type in that he thinks he more valuable to the fed then they are to him. These guys always feel they've been wronged and because of that it's less about money now and more about principles.
Although I wouldn't be shocked if he had a change of heart if he gets demolished.
All that said theres no question he'll be back, it's just a matter of time. The sooner the better though.
I used to think along those lines, too - but, after seeing Bret, Bruno, and Ultimate Jim go in, it seems the only claim we can make with certainty is that EVERYBODY eventually goes in.
And, I don't consider that "selling out," either. As I've mentioned here before, selling out to me suggests abandoning your moral code for a cheap payday.
Using Bruno as the most extreme example, he asked for a lot more than he thought Vince would ever agree to pay. That made it worth it to Bruno. Yeah, we could say that McMahon paid him off and Bruno caved in. But, in this instance, it may be more accurate to say that Bruno held out for a LOT of years, making VINCE cave in and pay a lot more than he was planning.