8. Jericho Drumm
It's still way too soon to be discussing potential legacy replacements for Doctor Strange, given the character only first appeared on screen midway through Phase Three, but it's also never a bad time to remind people that he isn't the only person to have held the title of Sorcerer Supreme.
There was the Ancient One before him of course, but other characters have also become the Master of the Mystic Arts both before and after Strange assumed the mantle, including most recently Loki.
The God of Mischief was in no way the right candidate for the role (and he only got it anyway thanks to some classic Asgardian trickery), but there was one supernatural hero who was able to succeed Strange - even if it was for a brief while - and that was Jericho Drumm.
Drumm is another powerful sorcerer who could join Strange in a third film, having taken on an increasingly prominent role in the Marvel universe in the comics over the last decade. He's a powerful sorcerer who's probably in need of a bit of an update, as far as his powers and superhero namesake are concerned, but he'd be a great presence to have in the MCU all the same.