I don't think Punk V. Taker will happen if Punk keeps the belt. Undertaker isn't going to lose to Punk because WWE would lose the HUGE pay day on Taker V. Cena for next year & I also don't think Punk will drop the belt until Wrestlemania, this run is so long that Wrestlemania is the only place prestigious enough to end his streak. It would be lackluster if he lost it anywhere else besides RR. Undertaker won't work a large enough schedule after WM to be the main champion of the company and Ziggler can't cash in on the WWE title, only the WHC.
Punk V. The Rock 2 (WWE Championship) (I think it's obvious The Shield will save Punk at RR claiming The Rock has done nothing to deserve his title shot over guys who have been working their ass off all year for a title shot. The interference will lead to a Wrestlemania rematch)
Brock Lesnar V. Triple H (obvious)
Sheamus V. Randy Orton (World Heavyweight Championship) (Orton wins the title & Ziggler cashes in right away and takes it from Orton setting up their 2013 fued)
Undertaker V. ??? (I'd love to see them use this year as a filler year and maybe let Wade Barrett be put in the same position as Orton was a decade ago. It'd help the roster out, I'd imagine it'd be less strain on Taker physically so he could possibly work a couple dates in 2013-2014 like SummerSlam and RR to build up a Cena/Taker fued for WM 30)
Big Show V. Ryback
I don't know what they're going to do with Cena. He's involved in so much right now. Involved with both Punk & Rock, Ziggler & I wouldn't be surprised if he somehow gets involved with The Shield after The Royal Rumble. Also, I guess this means I'm picking Orton to win the Royal Rumble.