Why should he change what has made him so successful? Kids and women love him, men and the so-called "internet smarks" hate him. Whichever way it is people have a vested interested in every John Cena match.
He arguably sells the most merchandise for WWE - why should he and the company risk affecting that?
I'm not a huge fan of Cena. Say what you will about him but you honestly cannot tell me you haven't been excited about a PPV main event (with the exception of the series against Khali) when Cena has his title on the line - you either want to see him retain it, or you want to see him be defeated and possibly have his head ripped off. You only need to hear the crowd during each of these matches to see the strength of the reaction he gets.
He's definitely improved so much this year. If you did a list of the top 10 matches from this year, Cena would be in at least 5 of them.
- vs Umaga - Royal Rumble, Last Man Standing
- vs Shawn Michaels, Wrestlemania 23
- vs Shawn Michaels, Monday Night Raw (their 60min epic)
- vs Bobby Lashley, Great American Bash
- vs Randy Orton, Summerslam (My choice for Match of the Year)
All these are 4+ star matches - he helped carry Lashley to the greatest match of his career. The one against Orton it looked like Randy was trying to take Cenas head off with each headlock and the crowd was deafening.
Its a positive that the title reign is over, and we do get new life injected back into the WWE, but an injury like this isn't how a 13 month reign should end - after No Mercy there was supposed to be Orton v Cena IV but this time it'd be Hell in a Cell - now we won't get to see that.