The creator of 'One Piece', Eiichiro Oda, had mentioned in the past that the manga was around 80% complete, but he did not provide a specific timeline for its conclusion. The manga made its debut in Shueisha's Weekly Shonen Jump in 1997 and stands as one of the most widely acclaimed and beloved manga series to ever be released.
At that time, the "One Piece" anime was in the middle of adapting the Wano Country Arc, which began in 2018 and was one of the most significant arcs in the series. However, remember that in the manga the story is more advanced since it is the base material.

In the manga, One Piece is in the "Final Saga" and this confirms that it will be the final part of the story, but let's not anticipate anything, since this saga can have several arcs, right now, it starts with the "Egghead Arc" .
When will the One Piece manga end?
As hinted by the creator Eiichiro Oda back in 2019, there are expectations that the One Piece manga will reach its conclusion around the years 2024 or 2025. Eiichiro Oda expressed his intention to wrap up the series in approximately five years, which would point to this timeframe.
Additionally, he disclosed that the manga is anticipated to encompass slightly more than 100 volumes, with 106 volumes having been released at present. He also revealed that he had been contemplating the manga's ending since his college days.
As mentioned by mangaka Oda, he has a strong desire to delve into additional narratives centered around characters such as Monkey D. Garp and Monkey D. Dragon, even though these characters play relatively minor roles in the series.