Several points that make me think that Shanks is the Yonko who owns Elbaf’s island.
In this theory, I will claim the points that make me think that the protector of the island of Elbaf is currently the Yonko Shanks.
I – New World Territories Functioning
Elbaf is the island of the Giants species in the New World.
The islands of the New World we saw till now are:
– Fish-Man Island, under the protection of the Straw Hat Pirates (previously under the protection of Big Mom and before that under the protection of Whitebeard).
– Punk Hazard, under the protection of Caesar Clown, linked with 2 Yonkos and with Doflamingo (previously it was owned by the World Government).
– Dressrosa was under the protection of Doflamingo. Now is owned by the World Government.
– Zou, independent island but led by Nekomamushi and Inuarashi, former pirates of Whitebeard and Roger.
– Totto Land, under the protection of Big Mom.
– Wano, controlled by Kaido who took it by force.
In the New World, most of the territories are owned by the Yonkos. Elbaf is foreshadowed since a long time, and the Straw Hats will go there for sure.
But it’s hard to tell how this island works, who owns it. I believe the most evident Yonkou candidate for this is Shanks.
II – Viking’s Thematic
So, basically it’s pretty obvious that the Giants of One Piece are inspired by the Norse barbaric explorers: the Vikings and their mythology.
Gungnir is the spear of the god Odin, chief of the Norse Pantheon.
The epithet of Shanks is “Red Haired Shanks”.
First, his inspiration comes from “Calico” Rackam Jack, famous pirate which the flag inspired Shanks flag for the Red-Haired Pirates.
But also, Shanks is inspired after Erik the Red, a Norwegian Viking.
The “classic” ship of the Viking is called a Drekar. The bow with a shape of dragon.
It’s basically what Shanks possess: the Red Force.
Also, look at the ship and the flag of the original Giants Pirates crew:
Lastly about this, I’ve found from some french theory I will link at the end this connection :
Shanks is also inspired after the god Týr, associated with law and heroïc glory in Norse Mythology.
Tyr is a one-arm character who sacrificied his arm to the monstruous Wolf Fenrir.
Remember the Sea King and Shanks sacrifice?
III – Similar view with the Giants
Shanks showed since the very beginning the “spirit” of One Piece, about freedom, adventure, pirate’s life and honor values.
Shanks is someone who respects what he says and had honor values. He’s brave and respectful. He likes to fight, act, travel, make parties and enjoy time.
He is a proper “good” pirate.
Something what the giants do share.
Sometimes, the Elbaf’s giants were depicted as “barbaric” but this was the point of view of Jaguar D. Saul, from the Navy who understood the real barbary because of the World Government decision.
But, from Usopp perspective and Elbaf’s giants themselves, they look like good people.
Shanks is a man who trusts in dreams, avdentures and will. He’s the symbol of the conquest and the wish.
IMO, the Giants from Elbaf share the same feeling about life.
IV – Usopp and Yasopp’s connection to the Giants.
Yasopp is one of the top fighters of Shanks, he’s a trusted man in the Shank’s crew and took the choice in his life to go to adventure and flee from his life with his wife and his son.
I believe the Usopp’s fascination for the Giants and the aventure’s desire comes from his father.
In my opinion Usopp will meet his father in “his” arc : Elbaf’s arc. So, Shanks crew in Elbaf could be the best shot!
*Theory by Zero Zero No Mi