He has to. If he doesn't, his match with The Rock doesn't work.
This is part of the problem of announcing a match like Rock and Cena so far in advance. While the Rock has kept fans interest peaked and Cena has done his part, it has ruined any feud that Cena has been in because fans know one thing.
There is no way Cena is going to lose or make a serious change to his character because at WrestleMania he has a match set.
While most fans who draw these conclusions are smart enough to know this anyway because of Cena's market value to the company and the history of his feuds, it doesn't help his character or the product.
That is because the WWE hinges on one thing: suspension of disbelief.
Of course Kane isn't a monster who has harmed Zack Ryder and can summon flames from Hell. It's as realistic as Jedis or the "realistic warfare" in a Call of Duty game. None of those are real, but that doesn't stop fans from enjoying them and casting their doubt aside.
The only way it works is if the situation answers one question: Do I believe this is real?
Real doesn't have to mean something based in reality. It just means that based on the rules of the company or show and the characters in it, everything makes sense.
While the Cena-Kane story angle does that, it is ruined by the future reveal that The Rock is going to face Cena in one month. It shatters the illusion and makes it hard for fans to sink their teeth into a brutal ambulance match when Cena has to be cleared in a month to make the WWE big money at their largest event of the year.
Unless the WWE pulls a massive swerve and shocks fans, it won't change what has to be the outcome.
And just like Cena's market share, the fight with The Rock has too much revenue in it and too much marketing sunk into it to be thrown away now.
Cena and Kane is an interesting match. On its own, it could have made fans wonder who would be left standing.
With WrestleMania a month away, the answer is already clear and with it, the trick is exposed.
It gives away the answer to who will win without a shadow of a doubt and leaves some fans without a reason to buy the pay-per-view.
Matthew Hemphill writes for the MMA and professional wrestling portion of Bleacher Report. He also hosts a blog, elbaexiled.blogspot.com, that focuses on books, music, comic books, video games, film and generally anything that could be related to the realms of nerdom.