#4: Brock Lesnar
Okay, so this one is a bit of a leap. Most fans are tired of Brock Lesnar's run as Universal Champion, and if the company decided to go cold on the idea of Roman Reigns or Braun Strowman going over Lesnar clean, then John Cena might be their next best.
Lesnar has destroyed everybody over the last 16 months, and there is literally no-one, except for maybe Seth Rollins or Bobby Lashley, left for him to face. If the WWE decides that Reigns or Strowman isn't the person to end his reign, then John Cena may be the only viable option.
Cena and Lesnar have exchanged victories several times over the course of their careers, and while Lesnar may have destroyed Cena in their last outing, there's no reason why John couldn't overcome The Beast in a rematch.
The match is also guaranteed money, and with the fans beginning to turn on Reigns more and more, a record-breaking victory from John Cena might be their next best option.
Of course, there is also Braun Strowman lurking in the background with his briefcase, and a match between Cena and Braun later down the line could also prove to be a big money-maker for the company.