All In
CM Punk is doing an autograph signing twenty-four hours before All In, in the same city that the event will take place - and he's also rumored to have been backstage during the recent All In press conference. Surely that can't be a coincidence, and given the nature of his commitments to other promotions and companies, there's no real reason for him not to appear.
He'd be in his hometown, he'd get an absolutely huge pop, and there are several guys who are already scheduled to appear that he could have some kind of showdown with. It doesn't need to be anything big or spectacular, but even hearing his music play and seeing him come out would be a cool enough moment.
Professional wrestling fans miss him, and they deserve to see him inside the squared circle one more time.