One thing about wrestling is that you can never say never. The only thing you can say for sure about the business is that nothing's for sure.
I didn't think Shawn Michaels would ever wrestle again. He just came back after eight years to compete. I always thought Daniel Bryan was done for good and getting back into the ring would lead to serious health problems. Now he's the WWE Champion. Paul Heyman had no interest in coming back to the WWE after the way things went down in 2006. Now, he's one of the most important parts of Brock Lesnar's act.
I'm not going to say that this means Punk will definitely come back one day, but a lot of strange things have happened in this business. If he really wants to and he gets the itch to do it again, and egos are put aside, he can always get back into ring shape and work less than he did before. In 2018, he has no interest in wrestling again. In 2023? Who knows?