On the grave stone Zoro is sitting on is written 944 and there are zombies hanging around with the Straw Hats.
If you take now the numbers of 944 and write them backwards to 449, you get the chapter 449 where you can also find a color page with…a dragon on it, which is clearly another foreshadowing for the Wano arc and Kaido:
The chapter is titled “The mysterious four of Thriller Bark” where we get to see the four major antagonists of the Thriller Bark arc Moria, Hogback, Perona and Absalom. I think that Oda was foreshadowing the reintroduction of Moriah and his companions since chapter 449.Moriah fought against Kaido in his prime and lost all of his crew, we also know that Luffy needs an huge powerup so maybe Moriah will come back and bring us nightmare Luffy back. The chapter 944 would also perfectly fit in the timeline of the arc.