Cena's and Punk's abilities were never in a position to be questioned, but can Ryback help the other two look good? Even Lesnar, who's arguably the best monster the company has had, did some pretty good selling despite being an awesome monster. That's the step I'm most eager to see Ryback take. The art of wrestling is a combined effort to make everyone look good.
depends on how they want to work the match.
something like Kane/Bryan/Punk where Punk knocks out one (Bryan in that case)and for the rest of 8-10 min it is Punk and the other guy (Kane in that case) with a run in by somebody like what AJ Lee did.
something like Austin/Kane/Undertaker where it is pretty much a handicapped match (in this case would be Ryback & Cena jumping Punk)with little tension with Cena/Ryback.
repeat of Summerslam, where Big Show dominated the match (what Ryback would do) and than handicapped. Than was hit with AA by Cena and is robbed by Punk cheap win (in this case it would be one of Cena/Punk since Ryback ain't getting pinned)
or a traditional triple threat where they are all getting their asses kicked equally. And the winner is whoever lasts the longest.
I tend to go with a repeat of Summerslam with Punk pinning a shell shocked Cena or No Way Out with Punk & Cena going at it and in the process ending their feud once and for all (or at least till next year