Well I already said that if the fights don't spill over into Wano, this will be Zoro's final battle. But I still think the chances are high that they do spill over into Wano.
CP-0 has made it clear this chapter that even if both KaIdo and Big Mom were to fall on the rooftop, it still wouldn't stop the inevitable outcome of the Pirate Alliance failing due to the vast difference in numbers, and the executives. On Wano there should still be plenty of capable Samurai left, who would join the fight if they see a rebellion, that can equalize the number difference.
Right now, you have Marco taking on King and Queen at the same time. No matter how strong he is, he can't defeat two other Yonko Commanders on his own. This isn't even to mention that Jack is recovering at the moment, and will be back into this fight soon. Nobody on the rooftop will be in any shape to go on and fight the remaining executives if by some miracle they pull off a victory against two Yonko.
Speaking of defeating the executives, Oda has never had the final Boss of an arc fall before their underling. Hard to imagine he will have both Kaido and Big Mom fall, and then turn around and have the executives fall
after them. So then do they fall first? How? King, Queen, and Jack are Yonko Commanders, and Zoans, they can fight for days on end. Are they meant to fall within this 10 minute time period that Luffy has to recover? The chances of that are less than zero.
There is also the fact that Oda has given almost no focus whatsoever to the downstairs fights. Are they really going to get off paneled?
How much longer can the Worst Gen on the rooftop hold out in order for Jack to recover, and then King, Queen and Jack all get established fights to be defeated? What about Luffy's proclamation about punching Jack in the face one day? Did Oda forget about that?
I can keep going, but I have to get ready for work. But like I said, if the fights don't spill over into Wano, this is Zoro's final fight, but I honestly just can't see how Oda will pull off keeping the battle contained to Onigashima when there is so much quastionable stuff that would need to happen in order for the Pirate Alliance to pull off the win here and now.