Nasjuro taught Mihawk how to fight when the later was a kid to become the successor to Garling.
I think Mihawk goes back to Mareijoa at the end and one shots Garling and assumes the position becoming the second strongest combatant behind Imu himself
Sanji’s opponent is a member of the God Knights and the third strongest after Imu and Mihawk at EOS Sora the warrior of the sea from the Germa comic and will have his own raid suit to parallel Sanji