No one knows the exact number, but there are still quite a few One Piece arcs left if you mean the manga/anime story overall. Recent coverage of the live-action adaptation notes that the story is only around the Arabasta portion so far, with many major arcs still ahead, including Sky Island, Water 7, Thriller Bark, Summit War, Fish-Man Island, Dressrosa, Whole Cake Island, and Wano.

What that means

The answer depends on whether you mean the manga/anime or the Netflix live-action. For the live-action, the material adapted so far is only about 13.1% of the manga story, so there is a long runway of arcs left.

Best guess

If you’re asking about the main manga/anime , the safest answer is: probably several more major arcs, plus smaller sub-arcs inside them. One recent guide explicitly points to future arcs still ahead rather than a near- term ending.

Live-action angle

For Netflix’s version, Season 3 is expected to move into Arabasta , which is one of the next major arcs in the adaptation pipeline. That means the live- action still has a lot of story left even after the next season.

TL;DR: for the full One Piece story, think “many arcs left,” not just a couple.