#6 Pete Dunne
Pete Dunne has cemented himself as a supremely gifted wrestler with his three match of the year candidates against Tyler Bate and is currently looking unstoppable as the United Kingdom Champion. Just imagining the matches he'd put on with some of the main roster would be enough to want him to be called up.
Dunne has already appeared on the main roster when he confronted and beat Cruiserweight Champion Enzo Amore on the taping of Monday Night RAW in Manchester, England, but that was more of a one-off deal.
I think that Dunne's main roster call-up will depend entirely on how much progress is made in the UK show that the WWE has planned. That being said, Pete Dunne is young and if I were the WWE I'd be getting him on the main roster as soon as possible.