Why hasn't this happened yet?
The obvious answer is merchandise sales. The WWE would rather not risk losing the cash cow Cena has become. At what point does Vince McMahon decide the product may be becoming a bit stale?
There was a glimmer of hope for a Cena heel turn last year during his program with Nexus, but it was denied. The Super Cena gimmick may be over with kids, but has overstayed its welcome with the core demographic the WWE has always catered to.
When the 2011 Draft aired, I was glad to be rid of Cena (as I usually end up fast forwarding through SmackDown) but then we got hit with an Attitude Era type swerve: Cena is back on Raw after being a member of the SmackDown roster for two hours.
Here are five reasons the WWE, and more importantly the WWE fans need a John Cena heel turn