With Randy Orton being the "right" kind of heel, I see the whole Austin vs HBK thing from '97/'98. Orton is Austin and has turned face simply because he is so over yet his character in most ways shouts heel, heel, heel. Cena, like HBK is the supposed babyface but the fans are sick of the babyface schtick so they great him with boo's. But as mentioned he is a massive merch seller. I doubt Orton is the key after their massive feud last year I think they won't feud properly for a long while. I think one day Cena will turn heel, but it might be too late by then, I think the next 12 months is the ideal time, before people just stop caring, how you would turn him heel I'm not sure, an attitude adjustment to a 5 year old comes to mind.