JR seem weary of answering this question, but answer it, he did.
“Will John Cena become a ‘villain?’ I get this one all the time. Same answer. I don’t see it any time soon. I wouldn’t do it. The guy sells too much merchandise plus he is beloved by a significant section of the audience including younger fans and ladies. I would not tinker with the company’s top guy simply because some male fans want it as many of the same also regularly espouse the virtues of PG-14. IMO, WWE doesn’t need TV-14 to be a success or for Jon Cena to become a hated villain…..for my two cents.”
I’ve been scoffed at for saying something similar, but oh well.
Source: JR’s blog