I can see Orton being the leader of Nexus. Randy will RKO Cena at Survivor Series, make Barrett lie down, and making Cenas unconscious hand count three, therefore getting Cena fired. Nexus will come down and attack John, and Randy will punt Cena in the head for good measure. Then the next night on raw he will say that he formed Nexus to help him win the WWE title and keep it. So when they attacked at Fatal 4-Way Sheamus happened to cover Cena first, and he ordered Nexus not to do anything about it before the match cause he didn't want to look suspicious, the reason they beat up Randy on Raw, they were hoping Cena would snap and he would be fired, as he is a threat to the title. It would also explain why Orton RKO'd Cena after the Bragging Rights match, because Orton was going to make Barrett lay down, but Cena made sure Wade won.
Then after a few months, Cena gets his job back the same way Nexus got a job, tearing shit up. Which will lead to Cena vs Orton at WM for the 9001th time. Just guessing.