Option #1 - John Cena plays the "Reluctant Follower" again...
Probably the most likely option. Ever since Hell In A Cell 3 weeks ago, John Cena's been forced to play the reluctant follower role, being forced to take orders from Wade Barrett, or else be fired. (Yeah, I don't believe that Anonymous GM for a second either...) Anywho, this is the simple thing to do for the WWE to add length to this storyline, especially if they are planning to put the Championship on Wade Barrett.
Now me personally thinks that putting the Championship on would be a bad idea right now, but I could very well see it happening. The feud with Barrett and Cena doesn't really need it, but it would be an automatic way of making it seem more important. However, if Orton was to retain, this option is harder to work, as despite Cena following orders, Barrett would fail in getting the Championship...Maybe it would lead to Barrett taking his anger out on Cena, further leading up to what looks like a Cena "snap". This option makes that moment more of a slow build for Survivor Series, which I think is the most likely thing to do. (If you don't believe me, check out the Survivor Series 2010 Poster...)
Option #2 - John Cena "Snaps" and attacks Wade Barrett
Again, a very likely option for the Cena snap to happen on Pay-Per-View, even if I don't think it's the best idea. Why have the snap on Pay-Per-View in front of 250,000 or so thousand who's paying the $55 to see the show, when you do it on RAW in front of 5,000,000 or so? It would make more sense, and I believe it would guarantee Survivor Series (November 21st) would get more buys. Trust me.
For this to happen, I think Orton definitely has to retain here. Barrett getting the Championship, only for Cena to attack him would instantly diminish his reign, even if it would lead to a Barrett/Cena Feud for the Championship. It could very well happen, and I'd have no major complaints if it did, it would make sense. Will it happen? Strong possibility.
And the other option is definitely a long shot, but it could very well happen...
Option #3 - The Infamous John Cena "Heel" Turn
Well, this is definitely the long shot for me. Especially after the story of Cena resisting the urge to beat seven shades of blue hell out of Barrett. It would also be the hardest to try and set up and make sense of it. Why would Cena go from swallowing his pride and resisting the urge to destroy Barrett to being alinged with him to win the Championship? That's why I don't see it happening, but this is the WWE, it was surprising enough when Cena lost at Hell In A Cell.
Don't count on it, but I've seen stranger things happen.