Cena is still the top guy in the WWE by a long shot. The vocal majority on these boards are not even close to the vocal majority who makes the WWE money. We get it, in the internet world, everyone hates Cena. In the internet world, everyone thinks Daniel Bryan is the greatest thing since sliced bread.
Outside of the internet world, things don't work this way. Little kids still have daddy buy the Cena gear. Little kids still don't know that the guy in the maroon trunks who keeps beating the Miz was an indy legend, he's just some goober who has a little difficulty on the mic.
For the most part, the majority who frequent these boards aren't the ones who Vince is targeting to make money in the first place. So while Cena may be stale to some of you here, and you think he needs a heel turn, reality says that he's doing just fine and Vince likes him just where he is. I'm not saying he should or shouldn't make a heel turn, I am just saying it may not be in the best interest of the company to have him turn just because a couple of overgrown kids on message boards don't like him.