Looks like it will indeed be happening. I just saw a video of Punk grovelling and apologising to Saudi Arabia in front of a bunch of Saudi fans who had been booing him. Gross. At least we can say that he's now just a brand rather than somebody with genuine morals. It was kind of obvious when he went crawling back to the 'E, but yeah, expecting to see him walking around with a MAGA hat on any day now.
With Cena, the reality is that to the majority of the fans he was, for all intents and purposes, a heel from the mid-2000s to the mid-2010s. It was a weird meta-heel kind of thing, but he was only a babyface to Vince, children and women. To male teens and men, making up at least 50% of the demographic, he was the most hated guy on the roster and it wasn't even close.
Cena as a cookie-cutter heel is meh. The novelty has already worn off. Cena as a 'cool' heel is fine, but it'll just end up the same as Roman where the fans will now cheer for Cena as if he's a face. Crowd logic has been warped for a while now due to the massive disconnect between WWE and their fans over the last 20 years - it's gotten better since Vince got the boot, but those fractures are still there and to some degree the traditional face/heel dynamic is probably forever altered at this point.
Only exception at the moment is Cody. I don't know if it's because he's so corny that it loops around into being sort of cool. Obviously AEW fans didn't think so, lol, but WWE fans are very different in terms of what they like.