Not everyone that boo's Cena necessarily want to promote hate along with Kane.
And on the flip side, if SOME want to hate on Cena they might as well earn a few bucks off it too.
That's where it's a win-win for the WWE. They're managing the Cena hate to the point where it's now a controllable angle, and earning a few bucks in the process.
The bottom line is if people really don't like Cena, face or heel ain't going to matter. They're going to boo him because if he's a heel, he's move set won't improve. And if he's a heel, it's going to be right back to Cena circa 2003 and that won't last long. It won't be boos because he's a heel, but because "Cena Sucks!" and that he can't wrestle.
The people who hate Cena aren't going to like Cena because he doesn't "give in to hate" and then keeps doing bad jokes. He's still going to be the same John Cena he's been for 5 years and that's the problem.
The only way this ends with a certain percentage of the fanbase booing less is less smarks boing him because they won't go to the shows to see a Kane/Cena match, so they aren't there to boo.
First off, the only reason Cena is hated so much isn't how he wrestles, that's apart of it to apart of the fanbase. It's his character that people boo, it's the bad jokes, the cheesy speeches.
And, again, you have a face who gets booed by half the audience minimum, and more than half on most ppvs. Heels often don't get booed because the crowd chooses to duel LEt's Go Cena/Cena Sucks, Cena gets booed more than the heel, that's not good for business either.
If the people cheering for Cena are really kids and women like it sounds, then making him go bad at least removes the kids cheering and then it sounds like he's getting a heel reaction.
And the reason i know this can happen is because i've seen crowds change on people in wrestling before. If they can boo and cheer Rock and boo and cheer Hogan and boo and cheer Punk (who, if you will recall, was often cheered when he was a heel, it didn't stop the kids from loving him on Raw) they can change on Cena.
It's ultimately just capitalizing on an aspect of the character that's somewhat unique to him. Fans hate on the guy... but they're still reacting very strongly to him, so it's not a hate that necessariy translates into a lack of interest.
When fans are quietly sitting on their hands while Cena is out there, then WWE has something to worry about. Right now, Cena still generates a strong reaction (stronger than anyone else heel or face), and still is a top by all standards WWE measures a superstar with.
He at this point should be a heel, imo, that tshirt is a test for it. Faces don't get booed as much as John Cena without turning.
And your lack of interest is year by year lowering ratings, lowering ppv buys, lowering merch sales. They need to do something new with him, because keeping him the same isn't helping.
"--Chris Hero will be working the 1/20 ROH show in Philadelphia. Hero is taking dates only a few weeks into the future awaiting if everything will be clear for him to sign with WWE."
And during Cenas time it has dropped lower and lower and lower, and it never goes up. Literaly every metric has dropped under him, not just ratings, but the problem isn't just Cena, it's the way they are using Cena.
Edit: a 4, for example, would be goddamn amazing.
Vince has a quote on one of the dvds, probably the wrestlemania one, where he wants to do something but his yes men say "Well,maybe we shouldn't because we could lose money" and Vince says "We can never grow unless we try new things."
He's lost that in his main product, he will blow millions on a network and say it's launching before it will be ready, but he won't even try to alter the character of his number 1 guy after half a decade.