We're 80-90% in the story in a Japanese-themed island in a Japanese series. Elbaf was hinted at since East Blue, but Oda wrote the 'Monster' one-shot before One Piece even existed. Let's recap what's happening here: (1) Luffy is given 2 weeks within an arc to improve himself, and so are others SHs. (2) Oda has gathered the majority of the Supernovas in one island (3) Big Mom is about to come to Wano (4) Other potential parties could include the Blackbeard Pirates, Whitebeard Pirates, Germa 66, the Fishman Pirates (5) Oda has confirmed Luffy will be the one to finish the World's Strongest Creature (6) Shanks hinted that Luffy is on the verge of becoming a 'great pirate'. (7) The Reverie will end 1 week before Wano - meaning the World Government has to time to prepare for a War against Kaido (8) Orochi is already getting cocky with the WG and making impossible demands (9) Kaido said he wants to start 'the greatest war the world has ever seen'. (ever seen obviously means up to that point not after that) (10) Oda potentially hinted that Wano will make MF look like a joke - this would be complementary to (9) We could potentially have all the 4/5 Emperors in 1 island with the World Government, Whitebeard Pirates, Germa 66/Fishmen all joining in massive wars. This is the arc where Luffy fulfills Shanks' promise of 'becoming a great pirate', the World's Strongest Creature falls, and feels the consequence of the Fall of the Shichibukai.