The Rock confirmed he will be in Miami for the May 2nd RAW to celebrate his birthday. I'm not saying WWE will pull the trigger on a Cena heel turn. I will say that you absolutely, positively, could not ask for a better environment/opportunity to turn John Cena.
It would be an easy story to write especially if Cena fails to capture the WWE Title the night before at Extreme Rules.
I doubt they'll do it, but that would shakeup WWE.