Yeah, but I hope that in the next chapters will happen something that can explain Ryokugyu's presence on Wano. Otherwise, Oda's management would be simply awful.
At least the BMP, maybe another scene with Shanks outside of Wano (with some importance).
If not, his introduction would be totally pointless. He could even have a Black Blade but no one in Wano, the land of Ryuma were Black Blades are a thing, said a thing.