I can't see it, R(ob)ie. Sorry, bruv.
When The Rock returned to WWE, it was the beginning of a four or five year plan that was made during the initial negotiations. Everything concerning The Rock since his return has been set in stone. Same goes for the next year or so. Hosting Wrestlemania XXVII, attacking Cena during the main event of Wrestlemania XXVII, the year long feud that was made possible and plausible by Rocky's sporadic appearances, the match with Cena at Wrestlemania XXVIII, beating Cena at Wrestlemania XXVIII, announcing that he would be facing whoever the champ was at Royal Rumble '13, beating whoever the champ was at Royal Rumble '13, facing Cena in a rematch at Wrestlemania XXIX.. All set in stone from the moment he decided that the time was right for his WWE return. Being the actor he is, he has had his schedule laid out for him with selective dates, and like the actor he is, he knows what he'll be doing on those selective dates. Each WWE appearance for him has almost been laid out like scenes in a trilogy of movies that has yet to pan out. His Wrestlemania XXX opponent has already been selected, and, if I didn't think that he would be such an excellent choice to face 'taker at Wrestlemania XXX, I'd say that it was probably Cena in a rubber match.
Back when CM Punk turned heel on The Rock with that infamous clothesline, it set the stage for Punk vs Rock at Royal Rumble '13. Punks reign was never going to end before, or after, Royal Rumble '13--all he was was a member of the cast in this "epic movie" type of deal that one of Hollywood's highest earners has cut with WWE.
I can't imagine Punk was really upset with his part, though.. Like, I'm sure it probably went down something like this.
"Wait, I get to be the champ for how fuckin' long?!?!!! Hells yes, VinneMacJr, I'm down wit' getting' me some 'a dat sheeeet!!"
"That's great to hear CM Mark."
"Wait, like, if I may, sir--who am I gonna be feuding with after I lose the belt to The Rock?"
"Well, I'd say that it's pretty much a certainty that you'll be getting a rematch with The Rock at Elimination Chamber '13."
**CM Punk mouths 'wow' before continuing.**
"And after that?"
"Well, the only logical next step after that would be a match with The Undertaker at Wrestlemani-"
*Vincent Kennedy McMahon Jr stops himself short at the sight of CM Punk fainting.**
Punk won't beat The Undertaker. It won't hurt him to lose, but would cost WWE a good few million dollars and then some if Punk were to win. The Undertakers streak being on the line at Wrestlemania XXX would generate so much interest and revenue, that they would be insane to throw that possibility away to appease a punk with a loud mouth.
Ideal Undertaker opponent at Wrestlemania XXX would be as I said Cena, where, Cena would end the streak, retiring The Undertaker. I mean, if they were to book Cena vs The Undertaker at Wrestlemania XXX, how could Cena not win? WWE isn't stupid, and it knows how the loss to The Rock at Wrestlemania would hurt their star player, but it also knows that a win in a rematch would be the perfect way to get his star value back. If he were to lose to The Undertaker at Wrestlemania XXX, there's no coming back, and that taint will be a permanent mark on their franchise player. Well, unless there was rematch, obviously, but, let's be honest here--why the fuck would he want to compete after Wrestlemania XXX. That would be the ultimate send off, and losing would be the best way for him to bow out in my opinion.
Failing Cena being the streak ender, then Punk should be the man. No other member of the current full time roster has worked as hard as those two over the past few years.