This thread is so full of fail...
Anyway, simply put, the person who will retire John Cena probably isn't in the WWE yet. Hell, the person might not even be able to wrestle yet. John Cena is like 30 years old, he's got 10+ years left. Hell, 90% of the current roster will be retired before Cena. Unless Cena goes off and does movies, but that's for another thread...
I don't think Cena will be retired in the way that Flair was retired, by an older wrestler. Because by the time Flair retired, he'd put over enough younger guys and didn't have much credibility. But Cena on the other hand will probably be main eventing till his last match and he should give the rub to a younger wrestler. Hence why I say the person who'll retire Cena probably isn't in the WWE yet.