the shield comes and helps Cena, then it's revealed he is their leader? nah, Cena is winning this one fair.
Last Rock/Cena promo, Cena said after he wins the title it'll change the face of the WWE forever.
Then on Smackdown, Johnny Ace came back and offered to be in Rock's corner but got the People's Elbow instead.
So I'm thinking Cena turns heel with Johnny's help. It's just a prediction but I can see that happening.