So. As of now, Cena is still undefeatable in the eyes of the world. His lost to the Rock is exception. Right now, Cena can retire as a 10 time World Champion who lost clean ONCE to the GOAT, in 8 years.
Also, Cena is extremely over and he will be over even if WWE removes him from their history for some reason(example:benoit). Which means that Cena's only real opponent for now is The Rock. If they continue the Twice in a Lifetime feud and Cena beats The Rock .. Cena will enter in the Stardom, looking stronger and undefeatable as StoneCold/Goldberg(example). After the whole saga, Cena will be out of high-status wrestler to feud with, which will lead to Cena putting over
. EEEEEK, that's the point of the whole thread. Cena can decide when to retire anyday of the year, so he can leave with his achievements, money and starpower without even putting someone over.
Cena is untouchable and im sure that he knows it. He still has the heel turn in his pocket. If he wants he can leave and go to TNA and im pretty sure that if TNA create a Cena Shirt, they will make enough money to use atleast pyros on their main PPV.