Depends. Marineford was only 30 chapters, though the number of actual, important characters was far fewer than what Wano has now. Also, a TON of character stories end this arc, namely Kaido and BMs crews in the least (the Yonko may or may not carry on, who knows), the Samurai and Orochi's side. This means we need a ton of dedicated panel time, like Dressrosa, to solidify everything.
Oda offpanels when it doesn't serve the story. As much as people hated it, Luffy training in Udon served the story, while Sanji vs. Page One lead to literally nothing, as evidenced by P1 being totally fine in Onigashima. This goes for every other offpaneled scene in the manga. Those characters will have their payoffs later.
As for Wano's war, im expecting anywhere from 40-60 chapters when the fighting actually starts, and it hasn't yet.