One Piece is always jokingly criticized as being a never-ending manga series. The Japanese manga series, written and illustrated by Eiichiro Oda began its serialization in Shueisha's Weekly Shōnen Jump magazine since July 22, 1997. The story of One Piece manga is been collected into 96 tankōbon volumes as of April 2020. Recently when Eiichiro Oda did a special for Fuji Tv, he announced that manga's end is near and that "One Piece would have just over 100 volumes total".
The question remains, when will One Piece end? And the upcoming volume of One Piece magazine gives a major hint regarding that. A leaked Black & White cover of the 10th volume of the magazine suggests that the manga is soon entering the final Arc.
In one of the threads from the forum named Worstgen, a user named Lance_Dragonite shared the cover and translated the text written on it.
As per Lance_Dragonite's translation, the title phrase is "Now is the time to re-read One Piece for the final section in future".
He translates the text beside Ace's picture as:
"The more you know the more you’re into it.
Re: One Piece
There are about 190 items in the checklist"
In recent Chapters, Kaido has joined hands with Big Mom and have initiated his step towards the great war. The cover text clearly hints that the next arc after the Wano Kingdom arc will be the final arc. The Whole Cake Island arc ended in the 90th volume of the manga. The current Wano arc is long enough to have at least more than 5 volumes, so with the end of Wano arc, the manga already reaches or almost reaches 100 volumes. As mentioned earlier Oda sensei had revealed that the manga will have just over 100 volumes. So by connecting these two dots, we can deduce that the next arc will be the final arc of the long-running manga One Piece.
A Reddit user u/ussopsenpai too shared (Which is taken down by the moderators now) a post in a subreddit of One Piece, pointing out that its "almost the first time when the manga is officially promoted as if it is near the end".
The cover of the magazine also suggests that the magazine will reveal the people who witnessed the execution of Pirate King Gol D Roger. The thread for One Piece Magazine was started by user ScotchInformer in the Worstgen Forum. The user shared one of the leaked raw pages from the magazine and revealed that the magazine talks about Ace's Novel Manga. The illustration for the manga is done by Boichi while Ryō Ishiyama handled the storyboards for the same. He also gave out that the 10th volume of One Piece magazine will be released on 4th September 2020.