In one interview last year Eiichiro Oda stated that One Piece will likely reach its ending in 5 years. This confirmed by his editor recently, that in the current pace the manga currently is moving, an ending in 5 years could happen.
Eiichiro Oda is known for terrible time prediction. Oda always expects things to take less time than they can take realistically. He originally planned One Piece to have a 5-year run, but it's serialized for more than 20 years despite Oda stating he's still going for the ending he originally planned. He also said once that Straw Hats would reach Fishman Island "soon," only for it to take 2 years in-universe. 5 years in real-life. They took several arcs of detours before they finally reached their destination.
That's why, when he said that One Piece is ending in 5 years. Most of the fans, me included, didn't thought too much of it. Oda's time estimations are always off. But when the editor says so, we can't help but believe him. Especially since they roughly knows what is roughly left of the story and editors are generally better at estimating time than Oda.
We don't want a rushed ending!
I'm more worried about ONE PIECE ending in 5 years... Not because I don't want it to end, but because the manga seems very rushed recently and for it to end so soon, it might have to be rushed even further to wrap things up.
Halfway through Wano arc, manga chapters starting moving at double then triple the pace they originally moved at. Many fights are happening off-screen now, and the ones we see are ending way faster than the fights we were used to.
Most of the fans think that 200 chapters are to little to wrap all the loose ends. Even though the main three mysteries of ONE PIECE are connected and could be solved at the same chapter, there are other questions that need to be answered before that.
A big arc of ONE PIECE takes around 100 chapters. Which takes two and half years considering the frequent breaks Oda takes. So, five years from now means two arcs at most. I can't imagine all of them being enough to wrap all the mysteries in a satisfying manner. (Though I really hope for it to be the case.)
There are at least two new islands with anticipated arcs: Elbaf and Laugh Tale (formerly known as Raftel for English-speaking fandom.) I believe the only essential arcMany fans expect finding that ONE PIECE won't be the end of the series, and I'm with those who expect a long Final Battle arc after that, an Arc that I hope to last 150 chapters (more 3 years) alone to sort out all the loose ends.
That's why we are worried. Because all of us want the ending of our favorite manga to be an Epic arc that's is bigger with more impact than any big arc we have seen thus far!