There has been a lot of discussion on what will happen with Big Mom once she comes to Wano. However, I think she won’t arrive at all and to explain why, I need to talk about Blackbeard.
Who are Blackbeard and his crew in the story? They are Luffy’s and the StrawHats’ character foils. This has been established over and over again in the story. It first started in Jaya with Blackbeard and Luffy in the tavern.
Read that chapter again, it’s clear what Oda was doing. As we learned more about Blackbeard’s crew, we also learned that they resemble the Straw Hats a lot and that’s because they are foils.
We also know that Oda has a lot of world building elements: things are constantly going on in the world of One Piece, it’s not like the world revolves around just the Straw Hats unlike in many stories. As Luffy was escaping Impel Down, Blackbeard was invading it. As Luffy was beating Doflamingo, Blackbeard was raiding the Headquarters of the Revolutionaries. There’s this back and forth in their actions too. Then that leads to the question: what is Blackbeard doing now?
He is going to track Big Mom in the sea and beat her! We know that Big Mom’s call with Kaido was not encrypted so we can assume Blackbeard knows too.
Furthermore, Blackbeard always seems to be a bit ahead of Luffy: he beat Ace while Luffy never did, he has two devil fruits, he became Emperor first. So if Luffy takes down Kaido, an Emperor, then story wise, Blackbeard has to do the same thing. He has to one up Luffy and how is he going to do that? Well, Luffy is probably going to get a lot of help with that final Kaido fight but Blackbeard is probably going to do it solo as that’s more his style while his crew will take care of Big Mom’s crew.
This makes more sense once you consider that Big Mom and Kaido were close in the past: they were part of the same crew or worked together or something. So as Luffy takes down Kaido, his foil (Blackbeard) takes down Kaido’s related Emperor. This also gives a reason for Katakuri/Big Mom’s crew to ally with Luffy in the future.
*Theory by Lopsided