It was also foreshadowed by the Cover Art of Chapter 784 in which zoro is sitting on a grave stone with the number 944 on it while wearing a shirt with a skull which symbols death and the word ultima on it which means final (which probably means the final act of wano). Previously people thought that this would foreshadow zoros death but we know oda wouldn't kill a main character, but recently the relased vivre card of Kaido has the number 0994 on it. Why would Oda choose this number on Kaidos vivre card? Coincidence? I don't think so. There is also another grave stone next to the one on which zoro is sitting where it says DECEMBER 20. Which means that Kaido will fall on that specific date.