Well he's also taking this break to revisit the story in preparation for the final saga.
I don't think there'll be many arcs left honestly, it's just gonna be:
- Elbaf (short arc like Zou)
- Laugh Tale (another short arc)
Then whatever he has in mind for the Final War. This is probably the only big war arc like Alabasta, Dressrosa and Wano he has left in store.
Yep, that's about the content most people expect.
Okay let's roll with it: If we go with your assumptions that these arcs happen and the first two arcs being a short arc like Zou (~23 chapters + a few chapters of room just in case) and if we take into consideration how Oda published about 38 chapters per year in the past years, then we can do the following estimation:
Elbaf ~30 chapters (~1 year) -> ca. 2023 done
Laugh tale ~30 chapters (~1 year) -> ca. 2024 done
Final War Arc (with Build Up): ~60~ Chapter (~2 years) -> ca. 2026 done
Conclusion (everyone dreams and stuff): 5 - 10 chapter? -> ca. 2026/2027 done
Odas 5 year anticipation: 2019 -> 2024
Our estimation: 2026/2027
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A few more notes from my site how I estimated things:
- Zou was written pretty straight forward, so if that's how the next two arcs are (Elbaf & Laughtale), then it would be in line with Oda speedrunning through these long anticipated arcs.
- Final war arcs are typically very long in shonen yet Odas wants to end things. I also looked at previous war arcs in One Piece: Wano has so far 144 chapters, while Marineford as a sole war arc had about ~30 chapters combined with its predecessor/build up arc Imple Down (25 chapters) it as a total of ~55 chapters. I just went with 60 chapters with Odas speedrun intentions in mind.
- Finally if Laughtale will be the build up arc to the final war we can even cut the final war arc in half to ~30 chapters and end up in about 2025 / 2026.
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Ultimately we don't know of course if this is Odas plan. He could choose a completely different route of islands/arcs or offscreen a lot of stuff to speedrun to the end. That of course would change the whole estimation. After all we can not say what Oda has in store. We can only see and wait.