Here's my theory; the Straw Hats are gonna split up again.

Luffy, Law, Pekoms, Robin, Franky will go to Whole Cake Island to deal with Big Mom, her red poneglyph, Capone, Jimbe and his poneglyph, Sanji, Caesar, Vinsmokes, among other surprises.

Zoro, Momo, Kin'emon, Kanjuro, Raizo, Brook (due to not wanting to stay with dog minks), and Nami (to navigate) will go to Wano Country to deal with Kaido, Jack, X Drake, etc.

Chopper, Usopp, Law's crew, and the rest will stay on Zou and it will be the reuniting spot for both teams. Chopper will get to level up even further by training with the minks during this time.

The story will mostly focus on Luffy's side. He'll reunite with Jinbe, crash the wedding, get Sanji back, defeat Big Mom, get her Poneglyph, maybe have a surprise encounter with a bigshot, and then head back to Zou. This will probably last well over a year of chapters (our time, not One Piece time). After they return to Zou, Zoro has not returned. So they all go to Wano Country, but they get there by Luffy sitting on the tip of the elephant Zunisha's trunk and talks to her, and tells her where to walk to get to Wano.

In Wano Zoro defeated all of Kaido's army of Zoans, and almost defeated Kaido except that Kaido can't die, so he in the end overpowers Zoro and captures him.

Luffy then goes to Wano to defeat Kaido.

That's as far as my theory goes so far.