Keith,
I understand that from a financial, marketing, and charity/outreach standpoint, turning Cena heel would've never worked, and probably never will happen. Setting those things aside, though, simply from a creative/character/storyline standpoint, do you think there was a HUGE missed opportunity for both Cena and Wyatt at wrestlemania 30? To have Cena snap at the end of that match and destroy Wyatt with a chair, denounce the fans, and embark on a heel run? And maybe a year or so later, have him and Roman Reigns team up as a hated heel duo that many of the fans boo relentlessly? All the while, Wyatt intensifies as a weird, antihero cult leader over time?
So…you're saying John Cena should have turned heel. Interesting. We should explore this idea more sometime.