#2 It's too predictable
Nobody who says they're leaving pro wrestling forever actually leaves pro wrestling forever. Whether a guy retires 10 times, leaves the business on a sour note and swears never to return, or shuts themselves off to the world after a quiet exit, more often than not that person shows up again at some point.
What if Punk stands by his word? He was adamant that he was done with professional wrestling, WWE or otherwise. He cut pretty much every wrestler, even close friends, out of his life. He has done nothing relating to pro wrestling (with the exception of Starrcast before AEW's All Out event) for more than half a decade. He's made it this far. Why not keep it up?
That's not to say that he can't return for induction to the Hall of Fame, for example. Vince McMahon produced an entire DVD that absolutely eviscerated The Ultimate Warrior, both the character and the man behind the paint. A few years later, WWE was releasing a multi-disc 'Best Of' DVD set for him, and he was inducted into the Hall of Fame as the star inductee. So it's obvious that Punk absolutely could find himself in a similar position.
It seems as though CM Punk is in a better place, mentally, than he was 6 years ago. Things are clearer. Maybe he has been able to look at things from a different perspective after being moved away from the epicenter of the problem. That could mean two things. First, it could mean that he's ready, as a person, performer, and employee, for a return. Second, it could mean that he's ready, as a person, a husband, and a man of many talents to keep true to his word and stay away from wrestling.
Very few people online have been fully convinced that he's going to stay true and never return. Maybe he'll prove them wrong. Now that is unpredictable for professional wrestling.