Cena no-sold a broken neck, he is like Angle minus the pill problem ofcourse. He will work through it, or take surgery and no-sell that. It's not just his elbow that is fucked up, it's his back as well. He has been working with herniated discs, there is a reason he take backbumps differently than most other guys on the roster,
He doesn't need to work everyday, but let's be honest here, he has nothing to really go home to, no wife, no children. His whole life revolves around WWE, I honestly think that isn't some catchphrase he says to get people cheering, pretty sure he actually believes that.
Fucked up thing is, he is bulletproof in his company standing, but if you're the king. Gotta watch the throne. Should take time off, give his face a rest, it's the time of year that WWE likes to experiment, give the belt to the little guy, see what kind of difference the fanboys of "workrate" make in terms of viewership and merchandise sales.