Responses
Nah, it will proplably take at least 7 years, maybe more. Dressrosa arc alone had 2 years, and we still have: fight with Big Mom, Kaido, thing with Dragon, finding about the Void Century, Shanks past, fight with Blackbeard, finding all poneglyphs, finding Raftel and One Piece and have a final war. And Oda is a master in slowing things up to have more fun :)
Given the current chapter, I could say that One Piece might end in 4-5 years from now. I'm looking forward to it and at the same time I'm not. From here on out there'll be a bunch of things to look forward to: Sanji's history, Luffy's reunion with Shanks, a showdown among the Yonkou's including the Dressrosa alliance aka Team Luffy, Marineford War version 2, and so much more.