Christian
Why it may be him – He was recently cleared for an in-ring return. He lives next door to Chris Jericho and if the WWE was going to incorporate him into their WrestleMania plans, they would have laid the seeds down by now.
Why it won’t be him – Seems like a strange fit as AEW likes to push young talent, not guys looking for one more match. It also seems odd he would finish out a career that the WWE made, with AEW.