Oda said “I’ll introduce one of the legends which lurks in One Piece world. The greatest enemy ever for Straw Hats will hinder their way. Perhaps it will be something related to Whitebeard”.
Kaido is already a legend in One Piece World. He is likely the main villain of the arc. And I think he had a relationship with Whitebeard. He cursed him for dying and he tried to attack him in the way to Marineford. But Oda himself said he was talking too much. And I’m afraid this is too obvious. So what if he is using a obvious hint to deceive the fans?
So, let’s say Kaido has 50% of chance of being the legend. And here goes a few theories.
SHIKI – 30%
Shiki the Lion is a canon character considering that he was mentioned in the actual story itself as he was the first to escape Impel Down. When Shiki escaped he went into hiding, meaning he fits the whole ‘Lurking’ role completely. Now, what would be his relationship with Whitebeard? Well, Shiki the Lion was one of the top 3 Pirates of his generation, just under Gol D. Roger and Whitebeard. It makes sense for him to have tried to ally with Whitebeard, and when that failed he would view Whitebeard as a rival that he needs to get rid of.
BLACKBEARD – 10%
It’s not my favorite choice, but I have a few reasons to believe that Blackbeard could make an appearance in Wano. Teach himself is already a legend, and we know he is trying to gather strong devil fruits. If Kaido has a strong (zoan?) devil fruit, I think he will try to get it eventually. And as the story goes, Oda needs to build up the rivalry between Straw Hat Pirates and Blackbeard Pirates.
GOROSEI SWORDSMAN – 10%
This is a long shot, I know. But actually it’s my favorite choice if it’s not Kaido. One thing that always intrigues me is the fact that some of the Gorosei have battle scars. We keep seeing them every time a big moviment occours in One Piece world, especially regarding Luffy. I think during Roger’s time this guys were also following the steps of the future Pirate King. I won’t be surprised if their scars are actually from fighting Roger himself or Whitebeard too.
And about the Gandhi Gorosei, the fact that he is a swordsman is already a reason for us to believe that he may have connections to Wano.
In his first appearance (chapter #233) he was talking about the Shichibukai. In chapter #594, he says his concern about the balance of the 3 great powers and again he talks about the Shichibukai. He also talks about the Ds and especially about Portgas. In chapter #793 he says the Marines are just the outward face of the World Government and he is suprised by the fact that Luffy, a “little brat”, is responsible for another huge event. And this event is related to the fall of another Shichibukai. Together with the other elders, he is concerned about the Ds. And when he speaks about Portgas, I think he means that not only the Ds are showing up too much nowadays, but Portgas too. In the past, Ace was invited for the Shichibukai, and if Gandhi Gorosei really is the mind behind the Shichibukai, he was the one who thought about inviting Ace, Roger’s son. A great move actually, trying to put the son of the Pirate King, a D., to work for the World Government.
I think Gandhi Gorosei will freak out when he knows that Luffy defeated Katakuri and caused a ruckus in Whole Cake Island. Morgan will tell to the world about this, and again a D. will be in the title of the news. It makes sense for him to act now, and I think this guy can be a legend in Wano for sure.
*Theory by Kouhei