If you ask me I am now more concerned by how it will end rather than when . It’s obvious that One piece has to end in like 8–10 years but if we take the War b/w Whitebeard and the navy as mid point as it should be. A well written good end would at-least take equal or I am more inclined to more time than the first half. That being said Oda is now rushing thins esp in last 1–2 years . And it is precisely because of this rushing the quality is rapidly deteriorating, check One Piece. There is so so so much content to be explored as things are.