So of the 8 quarter-finalists, six are important characters, one is a mysterious person and one is just a random trainer.
Who could that masked person be? Colress?
Maybe Black does win the tournament but at the end relinquish his title to Iris, who could end up being the runner up.
I'm Thinking the battles will be something like this:
Black vs Looker (Black wins)
Zinzolin vs Cheren (Maybe Cheren wins since in the games he helps Looker capture the sages)
Iris vs Young-Maniac (Iris wins)
Marlon vs Masked Man (Either one could win)
Black vs Cheren (Black wins)
Iris vs Marlon or Masked Man (Iris wins)
Black vs Iris (Either Black wins and relinquishes the title or Iris win)