This all parallels how Zoro and Sanji must evolve in the future to make Luffy Pirate King. Buggy right now has two warlords under him, while Luffy only has Jinbe. I think this will mean Hancock joining in the future is a must.
What does this mean for the two wings of the Pirate King? Zoro and Sanji would need to have a position above a Warlord, and that position is as a Yonko. Yes. Zoro and Sanji will become Yonko once Luffy becomes Pirate King. Sanji will take over Big Mom's territory/Buggy's position with Germa's army under him. Zoro would then take over control and guardianship of Wano with the Scabbards following his commands.
The Four Emperors at the end will be Zoro, Sanji, Kid/Shanks and Law/Blackbeard/???.
:cheers: