#5 John Cena
This is admittedly a long-shot, but the story is there. Cena hasn't appeared on WWE programming since he was decimated by The Undertaker at WrestleMania 34. He is still on the hunt for championship #17 that would see him surpass Ric Flair's long-standing record. Furthermore, Cena was absolutely destroyed at the hands of Brock Lesnar in the main event of Summerslam four years ago.
It would be poetic that Cena would want to make history against the same man and at the same event where he suffered one of the most embarrassing defeats of his career. The two Superstars combined have more than enough star-power to main event the show and Cena has been delivering consistently great matches ever since he made the transition from full-time to a part-timer.