if the injury was something that would keep him out for a long time, they wouldn't report it on dot com and they'd work a segment where someone is seen as responsible for it. Otherwise they'd be wasting a huge storyline opportunity on for unseen incident and no potential match up for Ryback.
All I can see is Ryback claiming he's destroyed Cena, him not wrestling until the event and then Cena winning.
It'd be good if it were a long term injury though, and they had to really come up with something good for the championship. But as I say, why then tell people he's injured out of a storyline situation.