While there is an air of a little bit of unpredictability regarding this match, probably not at much as Punk vs. Ryback, I still think think Punk retains. If you consider everything that's coming up in the next several months, I just don't see Punk losing the title.
The WWE has made Punk's streak as WWE Champion a big part of his character. With the one year anniversary of the beginning of his run just a few days away, it'd be a waste to have Punk drop the title tonight. Like I said, being a long running champ has become a significant part of who Punk is at this time.
Ryback has been doing well, probably better overall, now that the whole undefeated thing has gotten out of the way. Still, there's a lot for Ryback to prove. The only way any of the lingering doubts regarding Ryback can be proven one way or the other is with time and it not nearly enough has passed.
The Rock is waiting in the wings at the Royal Rumble for his title shot at the champ. While Ryback vs. Rock would lend an air of unpredictability to it, again, there's just not been nearly enough time for Ryback to develop the sort of presence to put up a believable feud against the Rock. It's only been during the past few months that Ryback has started to get over and putting him up against The Rock will almost certainly cast him in the role of the heel in the eyes of the fans whether WWE wants that to happen or not. They're gonna cheer for Rock and boo Ryback. If WWE wants to keep building Ryback as a powerful babyface presense, booking him into a feud with someone like The Rock would be counterproductive.
Cena could walk out with the title tonight but, again, I don't see it happening. If WWE wants a Cena vs. Rock rematch, it's going to happen at WrestleMania and not the Royal Rumble. RR is WWE's second most bought ppv of the year but WWE is wanting to get that third consecutive 1 million+ ppv buys and Cena vs. Rock II can help deliver it. With all the hype & build regarding their first encounter, having a follow up match happen 1 year later at the same event in which Cena lost the biggest match of his career just has a much better story behind it. Cena vs. Rock II at Royal Rumble 2013 doesn't have the same epic vibe as Cena vs. Rock II at WrestleMania 29.
On top of it all, I think just about everyone is looking forward to CM Punk getting his shot at Rock whether he wins or loses. Punk's been running The Rock into the ground for a while with comments, some of which have probably been laying the groundwork for a match between them, and we haven't seen Rock since CM Punk delivered the GTS on him at Raw 1,000 back in late June. With Punk being such a despicable heel these days and with so many people liking the idea of Punk possibly being put in his place by one of the all time biggest stars in wrestling history, it just sounds too good to ignore. There's a LOT of money to be made from Punk vs. Rock at the Royal Rumble, more I think that Cena vs. Rock II at the event and certainly more than Ryback vs. Rock.