Well first off it isnt the main event, this whole PPV is about brandwarfare. I think it's important to remember that when thinking about this match
Okay so we know like last year we will have a Superstars match and Divas match likely then a 7 on 7 to end it, a best of 3 matches and the trophy goes to the winning brand
then you've got the Divas title bout, World title bout and WWE title bout
I will say this- Wade Barrett winning, I'm cool with, ONLY because he's Leader of Nexus and Nexus is a cool thing that means something right now, but had he just won NXT and that was it I'd be like no
Atleast Barrett's win would be better than Sheamus' (who's first WWE title win I still hate, but who's grown on me as I thought he would) as Barrett has the story, and has a really good thing to get his win over- Cena being in his corner and a possible Nexus helping further, you basically can have it be believable and ok with a screwjob victory
But at the end of the day if you want the short answer to your question then here:
1. If Barrett says to Cena "Make sure I win the title, that's an order or you'll be fired" (fired cause if he doesnt do what Barrett wants he's gone, I think that will apply here as well, it should and likely will) Cena will have Barrett win no doubt
but if there is no added pressure on Cena then Barrett doesnt HAVE to win, but it'd seem like they'd have pressure on Cena that if Barrett loses Cena is gone because he didnt successfully fulfill Barrett's command, and that is the rule of being with Nexus in Cena's case
7 on 7 will be the last match though, not this one, and Nexus will surely crash the party, mark my word on it, this is what will cause both brands to create one team, 2 raw stars, 2 sd stars and having a 5th mystery spot for a returning star from injury or returning legend seems likely but it will have guys from both brands
5 on 5, Nexus will have Barrett, Justin, Otunga, Slater and Cena (Cena will turn on the Nexus)
Considering that actually Barrett may lose, not just because Nexus has a bigger match at SS than focusing on the title, I mean if Barrett wins whatever(they could have Barrett defend at SS but it makes more sense if he isnt a champion yet and fights with his team at Survivor Series)
So unless Cena's career is threatened I'm calling Barrett not to win