In my opinion, the 9 shadows being cast in Toki's prophecy are Zoro's "Kiki Kyutoryu Ashura" !
So I think Zoro will use it in the final round against Kaido while Toki's prophecy is rehearsed.
Then Zoro will not only behead him but, while doing so, he will also turn the dark sky into mist ... to let appear the rising DAWN