Cena will never turn heel.....he's the Hulk Hogan of the new era with the whole, "eat your vitamins, drink your milk, and say your prayers" routine.
He's the image of good, and until he finally loses all credibility as a relevant star who can attract and draw, like what happened to Hogan when he turned all nWo, and Bret hart all anti-American, he'll remain the "hero".
Like I said I don't watch wrestling anymore, but I still watch the headlines as to what happens on the WWE website.
CM Punk turning heel is better for him; it suits his character more, and I think he draws more attention that way.
Is Brock coming back anytime soon?