4-6 years left.
Suicide rate will spike in the young male generation then.
At the very least, I hope it's 5 years, when Luffy beat Lucci, it was in 2007, then MF arc and post war were in 2010-2011 and like that, the first half of the Series ended, it was after 3-4 years from Luffy's fight with Lucci, and now with Luffy vs Kaido which fans back then called it "Luffy vs Lucci on Steroids or like "Luffy vs Lucci 100.0" has finally ended, let's hope it'll take like at least 5 years to end OP which is in 2029, and also when it ends in 2029, it will be after 6-7 years from Luffy's fight with Kaido which were in 2022 in Mange and 2023 in Anime, which would make sense cause it'd be 30 years since OP when it was first released in 1999 and also to end the 2020's decade on a high note, you know? like MLP: FIM was from 2010-2019, it was throughout the whole entire 2010's decade.
Edit: also Oda can end OP quickly if he just stopped dickteasing the fans and every 3 chapters after 1 week, he waits for 2 weeks to release the next chapter and then the same cycle happens over and over again, 3 consecutive chapters each after 1 week then waits for 2 weeks and releases the new one and so on, instead, in these final 5 years, he should make the chapters every 1 week.