I'd say it's practically inevitable we see him involved again in some capacity. Will that be wrestling, to accept a HOF induction, an interview 20 years from now? Who knows.
History has proven though that almost everyone ever involved, especially if they reached the heights Punk did, will return at some point in time. If Bret, who was lied to, made a fool of in front of his hometown audience, and then had his brother die under their watch, would return…it's safe to say just about anyone would.
I think if his marriage with AJ doesn't work out, and/or his UFC and comic book careers don't go as well as planned, that will be when he starts to reevaluate things.
Honestly, I'm a fan of his, but if he never returns I'm not exactly losing sleep over it. I think his mystique has come from the way he left, not so much that he actually left. The year prior to leaving he was basically just spinning his wheels. He had already accomplished pretty much everything there is to do in WWE. He was certainly entertaining, but I can't imagine anyone puts him in their top 5 or anything. I think it would be kind of nice to see someone have some conviction and never return, but I guess time will tell.