As we know Ash didn't battle Marlon, but I will actually be really disappointed if Ash doesn't battle Drayden. He should logically be Ash's last trial before the league even if he has all 8 badges.
What I am hoping for is Iris battles Drayden first and then loses, and then we see Ash battle him and win.
What I am hoping for is Iris battles Drayden first and then loses, and then we see Ash battle him and win.