This. Folks can complain about Cena all they want, but as long as he is making Vince money, he's not going anywhere. Yes, his act is stale. Yes, he's been doing the same thing for 10 years. Yes, he could benefit from a Hollywood Hogan-style heel turn. But women love him, children adore him, and he still moves an insane amount of merchandise for WWE.
Until Vince can find someone who:
1) has Cena's all-American clean cut look
2) is well-spoken
3) carries himself well and won't get into trouble in this TMZ age
4) will become a total company man who will project a positive image of himself and WWE on talk shows and Make-A-Wish appearances
5) sells an obscene amount of t-shirts, baseball caps, wristbands, headbands, dvds, etc.
then you can expect to see plenty more of Mr. Hustle/Loyalty/Respect.