Let's really run down the list of headliners you have.. Rock, Triple H, Big Show, Taker, Goldberg, Batista, Cena, and Lesnar. Lets not forget still lurking as well to be headliners are Punk, Orton, Bryan, and maybe Kane. Triple H contract expires in 3 years as an in-ring performer and I don't expect him to re-sign. As for John Cena, while he will never leave WWE completely I don't see him wrestling much longer. I see Cena slowly becoming The Rock and just making pop ups here and there and wrestling every now and then while never officially retiring. As for Big Show and Kane, I think they're good as done and if Show's match with Strowman was his last then it was the perfect way to go. I would say that Show and Takers are locks to go in this year.
So getting to the 2018 class:
HEADLINER: THE UNDERTAKER
Tag Team/Stable: nWo (Hogan, Nash, Hall)
Mid-Card Name: Big Show
Women's Name/Deceased Competitor: Chyna
International Legend: Vader
Pioneer: William Regal
Non-Wrestler: Vickie Guerrero