You know what? Monet's defeat actually makes me excited to see what happens to Vergo. Because, in the past, I've compared this arc to Little Garden where a series of weak, cowardly villains challenge the crew for awhile, leave them on the ropes, only to get defeated in a such a way that we can't doubt that the Strawhats were way stronger to begin with. Now, I'd be happy either way, but can the same happen to Vergo? Is he as badass as he seems, much in the way Mr. 5 was before meeting Luffy, or will Smoker surprise us all and display a new level of power? I really hope we get to see this fight next.
I suspect Smoker takes care of Vergo, maybe with help from Law at best. The strawhats don't have any connection to Vergo so it makes more sense for those two to take care of him. If they do finish him off this arc.
But from the start I figured this arc would be another "overpowered" strawhats. The reason for this is because of the biological weapons. Only the weak resort to using weapons like that. You would never see Whitebeard or Shanks need to rely on a biological weapon. Ceaser is obviously not super powerful fighting wise if he spends so much energy on things like that. Take away his sucking oxygen and poison and he is pathetic. Another one of those Crocodile woudl label as "relying on their fruit" Then consider how easily Zoro took out Monet, all that's left is Ceaser and Vergo. If Monet didn't interfere it seemed Luffy would have already taken out ceaser. The only evenish fight at moment seems Smoker/Vergo.
So I see it being another Fishman Island, where the main problem is the biological weapon.