Even though Triple H is a likely choice for the ringleader, I just kind of don't care for that. Their are many more ways to get the eventual CM Punk vs. Triple H feud to happen. I can see Steph being the one behind this, and through Punk trying to get revenge on Steph, forcing Triple H to get involved and go after Punk. Of course, the actual match between the two will probably take awhile to happen, as I see the encounter at Mania, or maybe (this is probably more likely) this feud will go quicker and will culminate at Hell In A Cell with Trips vs. Punk.
The main reason I see Triple H getting involved in the feud with Punk to protect Stephanie over the option of being the mastermind behind this, because I don't see any reason why Triple H would screw John Cena over the title. At Summerslam, Stephanie was seen leaving John Cena's locker-room, and she didn't seem that happy. Which could lead to the text stating "Take out the winner of the match". The next we see here, she's with Triple H before the match. I guess I'm going on a limb here, but I'm saying Steph probably sent John L. sent the text while she was with Trips, and for the reasons stated above and to maybe a lesser extent Steph's position, he gladly did so. Then on Raw he went to get Nash a contract. Sure, Triple H is likely and all, but if he knew about the text, I'm not so sure why he'd let Nash come out and plainly state that Trips told him to do this. I just think Triple H is smarter than to completely throw his name in the loop. I think Triple H's involvement here is more or less, just a red herring. I'm sure through Punk-Steph, he'll get involved, but I don't think he was behind the whole thing.
Another scenario is that Vince is behind all this. Steph mentioned she talked to him before the show at Summerslam, and Vince has more than enough reason to want revenge on both Punk and Cena. I'm just throwing this one out here, as I don't see it happen. I honestly think we're done seeing Vince except for special occasions.