Why do people make a huge deal out of the Once In A Lifetime stuff? It was just a name to hype the match. And you can easily justify calling it that and because kayfabe wise, you could simply say that Rock and Cena intended to fight only once, but then circumstances (i.e Cena winning the Rumble, Rock winning the belt) lead to them facing off again. People actually mock the WWE by saying they could actually call it a Once In A Lifetime Rematch, but I could actually see them doing just that. Not that I'm looking forward to it, of course.
That said, I hope that Punk is entered into the match as well because it adds new life into the feud, not to mention he deserves to headline Wrestlemania given he's been a part of the main event scene since mid-2011. Not to mention his feud with The Rock has been pretty hot. No one would have ever thought Punk could legitimately feud with Rock of all people, but he has proven he can, and already long proven he can hang with WWE's current top star, Cena. Plus, while I can understand one rematch, I really don't want to see a third Rock-Cena match next year, and making the headline match this year a triple threat very much diminishes the chances of that happening.
The Cena/Punk match next week should be exciting because I really don't know which way they're going with it. It's either:
1. A no contest that leads to Punk being put in the match anyway
2. Punk cheats his way to victory but because he cheats, Vince decides to let Cena enter into the match anyway, similar to Rey Mysterio losing his WM title shot in 2006 but being put in the match anyway by Teddy Long.
3. Cena beats Punk, and that allows him to exorcise one demon, since not getting a victory over Punk yet has been one of the things bothering him. Finally obtaining a victory would give him a lot of extra confidence that he can also beat The Rock at Mania. Then Punk goes on to say he's gonna top Cena and Rock and being the WWE Champion by accomplishing something even greater and more worthy of remembering by defeating Undertaker;s streak. While I would love to see Punk in the triple threat, this is a pretty good set up for Punk/Taker as well.
And no chance that a fatal four way with Ryback is happening. That would be totally random, and it gives The Shield really no one to work a program with for Mania.