We must first talk about one major thing, do the battle in Onigashima end in a overall victory for some side? Are the battle in Onigashima the last battle with the outcome is the end of Kaido?
In my opinion it is most like not, as @dirtyLarry said in the past, the war/battle must placed in Wano so the people their could see Kaidos end. The people in Wano must get the hell before they can gain the victory. Also we are still in Act3 and that means in the kabuki theater a bad hard defeat for the heroes and a dramatic story(lose for the heroes) which even open more the result of a lose in Onigashima, how Oda gonna handle it, we gonna see it most like later.
But my speculation is based on a lose in Onigashima so my though:
Luffy vs first Jack(he want to beat him up)or Kaido Son(if he is stronger then a YC1 lvl character, I can even see Kid and Luffy fighting together to take him out) and after Kaido vs Luffy
Zoro vs Who´s Who(beating a calamity potential lvl character)
Sanji vs Pageone/xDrake
Jinbei vs Sasaki
Mid and low trio Shp vs Headliners/
RS vs Queen and King
No way that the Mid-Low SHp gonna face characters who pose a lvl to became a calamity, at least not in a 1on1 fight, they need most like a RS as major help to face them.
In my opinion it is most like not, as @dirtyLarry said in the past, the war/battle must placed in Wano so the people their could see Kaidos end. The people in Wano must get the hell before they can gain the victory. Also we are still in Act3 and that means in the kabuki theater a bad hard defeat for the heroes and a dramatic story(lose for the heroes) which even open more the result of a lose in Onigashima, how Oda gonna handle it, we gonna see it most like later.
But my speculation is based on a lose in Onigashima so my though:
Luffy vs first Jack(he want to beat him up)or Kaido Son(if he is stronger then a YC1 lvl character, I can even see Kid and Luffy fighting together to take him out) and after Kaido vs Luffy
Zoro vs Who´s Who(beating a calamity potential lvl character)
Sanji vs Pageone/xDrake
Jinbei vs Sasaki
Mid and low trio Shp vs Headliners/
RS vs Queen and King
No way that the Mid-Low SHp gonna face characters who pose a lvl to became a calamity, at least not in a 1on1 fight, they need most like a RS as major help to face them.
Zoro is also likely to eventually end up in the Flower Capital, where, like Ryuma, he cuts a dragon out of the sky. That could be as a conclusion to the fight with King, it could be him landing a last gasp hit on Dragon Kaido to get him out of the sky before him and Luffy finish their fight on land.
The majority of the battles are going to be in the here and now, on Onigashima, and will be won by the alliance. It's just going to be putting down Kaido that's going to seem impossible- we're probably going to see Kaido singlehandedly wipe out a ton of characters, albeit characters who have already fought and are exhausted. But the sinking of the ships, and the fact they've planned this raid to coincide with the full moon so the Minks are at full powers, shows that Onigashima is where most of the fights go down.
Basically how I think it will go
-fights in Onigashima, won by most of the Alliance. This is where we get Luffy, Kid and Law against Kaido
-a big twist with Big Mom
-Kaido wins, but his crew (except maybe King) are beaten. He flies off to Wano with Orochi in a rage to annihilate the Flower Capital
-a battered Luffy flies on Momo after him, maybe with Zoro. Whatever the case, we'll need Zoro to somehow get there as well.
-we'll get Zoro vs a dragon in the FC
-Luffy will beat Kaido there