Remember how great the "Two-Man Power Trip" was?
It was a tag team that we never thought we'd see comprised of Triple H and Stone Cold, both in their prime. Had Triple H not suffered yet another quad tear, there's no doubt these two would have had an unparalleled era of domination (provided Vince didn't prematurely break them up).
Why am I bringing these two up? Its simple. Cena and Punk could be the next version, and possibly a better version, if WWE will finally turn Cena.
Go with me on this setup. WWE books Cena and The Rock to square off against the newly turned CM Punk and Big Show at SummerSlam. Since Rock came to Cena's aid, it would only seem fair that they are at least somewhat on the page.
The match is going par to the course when, near the end, as Rocky is ready to drop the People's Elbow on Punk for the win, Cena grabs him, throws him in an AA and then leaves, as Punk pins him 1...2...3.
It's not until the next night on Raw that we find out that Cena didn't just screw Rock as a result of their past rivalry, but more because he's ticked off that Rock gets to just walk into the title picture after being gone yet again for several months. Cena reveals that while he doesn't always agree with Punk, he respects his work ethic and now sees that Punk is justified in his recent actions.
The two align in an effort to keep the belt off of Rocky since he will be facing the champ at the Royal Rumble. While Rocky is off of TV near the end of year, you let these two wreak havoc among the rest of the WWE as a legit stable/tag team. Let them take on Orton as a true face, Seamus, etc. You could even use them to turn current heels like Ziggler and The Miz into top faces.
By the time Rock returns after the first of the year, Cena/Punk have been legitimized as a terrible twosome. At this point, both Cena and Punk's characters have been rejuvenated by the move, and the crowd is squarely entrenched in hating them.
Rock finds a way to take the championship at Royal Rumble but then ends up having to face Cena and Punk at Wrestlemania 29, where he ultimately drops the belt. There you can either keep both guys heel or turn one back face; there are a lot of ways to go. But I think this could lead to fresher storylines for the WWE.
Another way you can strengthen this storyline is add in Big Show and John Lauranitis to the landscape. If you make "Big Johnny" the mouthpiece (cause the man draws massive heat) and Big Show as the enforcer, then you have a classic faction which could lead to the creation of an equally strong face faction (Orton, Kane, Ziggler, Miz, if I had to pick a few guys).
I just don't think there's a better way to go for the WWE right now as the product fights within itself to keep from becoming stale. It will freshen up John Cena's stale character and give Punk the chance to do what he does best: piss off fans and be the best in the world.
I know WWE will likely never let Cena become a heel due to merchandising and marketing. But I believe there would be just as many fans of a true heel Cena as there are of his overdone good-guy gimmick.