#5 Matt Riddle
Matt Riddle has only been with the WWE for a few months now, but through his feud with Kassius Ohno, he has been established as a potential superstar, and given his legitimate background and clear X-factor, it's only a matter of time until he's in the main event.
Riddle combines his legitimate MMA background with all the flair and charisma that's needed to make it in professional wrestling, and it's clear that he's got a big future ahead of him.
With the amount of stars down in NXT, Riddle is going to have to fight and claw to get to the main event, and considering his talent, he will be in contention for the NXT title soon, so the main roster may be over a year off.
John Cena has been the top guy in WWE for years now, and there's plenty of opponents who could take that spot from him, but in NXT, it seems that Matt Riddle is the safest bet, so this bout needs to happen.