I personally still think that 5 acts are possible, but therefore the third act needs to end like really, really soon. We're nearly 100 chapters into the arc.
If it ends with Act 3 i think Oda cancelled 4 and 5 because his jump message heavily hinted that he wanted to squeeze in some Sabo,Vivi, Hancock and even Shanks stuff and neither of them is coming to Wano.