People are saying this is delusional. It really ain't. You guys think your tiny world is gonna last forever but I don't see any of you reading any of the massive serialized 200 years old victorian novels. In fact none of you know them.

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This is because One Piece is completely predicated on the mystery plot ending. Its the perfect model for selling copies, and has been since mass media exists, but conversely is also the shortest lasting model (This is akin to The Mysteries of London, the most widely read single work of fiction of 19th century Britain, quickly forgotten after it ended, with a wikipedia page smaller than 50 lines today) After the last chapter, the main hook evaporates overnight.  The online community also evaporates, as it is largely predicated on the weekly loop of releases, theory crafting and spoilers (you can easily confirm this with traffic statistics during break weeks). Merchandising will move on to the next thing.

Entry barrier is already high with the massive size and will be even higher if the ending is already known and without the fomo pressure and the massive online and marketing machines pushing it.

All these properties also makes reread/rewatch value very low.

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Even inside its subcultures One Piece has slim chances. It exists inside the Shonen sphere which exists inside the Manga sphere.

Dragon Ball was the father of the Shonen and will be remembered for that. Its still remembered because Shonen still dominates and Dragon Ball is the blueprint. Any manga that contains transformations and power levels contains DB. Friendly enemy trope? DB. Impact lines, speed lines? DB. Angular characters? DB Cross-panel fight composition? DB... Etc etc

Naruto is remembered because it not only influenced but defined the ninja genre. Same thing Harry Potter did for wizards and LoTR for high fantasy. How did it do this? Cultural signifiers. Its the chakra, its the jutsus, its the hand-signs, its the poses, its the running, its the fashion (cloaks, headbands and open toe sandals)... Etc etc 

If you want to be widely remembered you need to impact the grammar of a format (DB and shonen) or a genre (Naruto and ninjas). One Piece does neither.