The WWE can live without Cena. Sure, he's a big draw, but like many others have said, big draw leave all the time and someone else just fills the void. Hogan/Savage left and Bret/HBK took over, Bret left and Austin took over, Austin left and Rock took over, Rock left and Lesnar took over... the list goes on. Hell, Cena is the one who filled the void for Lesnar when he left, and Lesnar, in terms of ratings only, was probably just as big a draw as Cena is today.
When big stars leave, most of the time their biggest fans just translate to the next big thing rather than pack up and leave. When Cena got injured a while back, the 'E rallied behind Jeff Hardy until Cena came back. They CAN make stars, believe it or not. Most of the time, though, they are just too scared to pull the trigger (ex. Ryder). If Cena left today, CM Punk (or probably Orton) would most likely take over as top face billing. And let's be honest, if Cena left, the 'E would probably see a small increase or at least a stagnation in ratings for a time, not because they hate Cena, but just to see how they fare without him.
And even if that big Face of the Company void isn't filled immediately, which has happened before, they'll capitalize on the biggest heel in the company and systematically build the show around him until the next face is made.
When big stars leave, most of the time their biggest fans just translate to the next big thing rather than pack up and leave. When Cena got injured a while back, the 'E rallied behind Jeff Hardy until Cena came back. They CAN make stars, believe it or not. Most of the time, though, they are just too scared to pull the trigger (ex. Ryder). If Cena left today, CM Punk (or probably Orton) would most likely take over as top face billing. And let's be honest, if Cena left, the 'E would probably see a small increase or at least a stagnation in ratings for a time, not because they hate Cena, but just to see how they fare without him.
And even if that big Face of the Company void isn't filled immediately, which has happened before, they'll capitalize on the biggest heel in the company and systematically build the show around him until the next face is made.