5. John Cena

He's the face that runs the place, the measuring stick, the Champ... and now, the part timer.
Much as men like Hulk Hogan and the Rock have done before him, John Cena has been splitting his time between pro wrestling and Hollywood. He had break out roles in such films as Amy Schumer's Train Wreck, and then starred as the voice of Ferdinand the Bull in the animated film Ferdinand.
Most recently, he has a co-starring turn in the Transformers spin off Bumblebee. John Cena is clearly a man with multiple priorities, but so long as WWE is one of those priorities don't expect him to fully retire.
Chances of winning the Royale Rumble: 50%
If Cena is interested in working Wrestlemania, he might just wind up the winner as a way to springboard him to the main event and to re-establish him with the WWE Universe.