At this point we've gotten quited used to Oda and the editors stating that the series will end within 5 years. One common misapprehension is that it isn't specified from what point onwards this supposed countdown would commence. Would OP end in 5 years
after Wano has been completed? Well then it isn't really 5 years. Would OP end in 5 years from when Oda first made that statement then we would have roughly 3.5 years left. I think the best method in measuring how long OP will go on is simply to look at the span of the Pre-Timeskip sagas and comparing them to were we are right now.
As you can see, the Pre-Timeskip part can be divided into 6 sagas each containing multiple arcs (Thriller bark is the only exception).
In the Post-Timeskip era Oda has maintained the same formula however the reason why the arcs were shorter in the Pre-Timeskip part is because the story structure was different, Oda introduces far more characters now and has to give reasonable screentime to each of them. Compare Alabasta to Dressrosa for instance.
Alabasta essentially revolves around the strawhats having to defeat Baroque works whereas Dressrosa involves far more characters than only the strawhats, this is why we ended up with so many fights from the colloseum fighters. The same thing is happening in the current Wano arc where so many factions and people are involved so it's only natural for these arcs to be as long as they are.
Let's say Wano ends in 2021. At this point Oda would have to do 3 more sagas which would be a minimum of around 5/6 arcs.
This is how I could see the story unfolding:
Elbaf Saga : transitional arc (short) + Elbaf arc (long) (60-80 chapters)
Raftel Saga : Loadstar Island (short) + Raftel (short/long?) (40 chapters)
Final War Saga : Final war (long) + epilogue (short) (120-140 chapters)
Given the fact that both Dressrosa and Wano exceed 100 chapters I feel like it would be a reasonable assumption to say that the final war arc would have to be atleast close to that number, especially considering that so many characters would get involved and that Luffy usually fights his opponents multiple times throughout an arc.
Let's do the math and assume the lowest number possible. 60+40+120 = 220
I personally believe this number would be higher considering that Oda usually tends to drag out the story and create suspense and build-up.
Now let's look at how many chapters Oda releases every year.
As you can see, the number of chapters that Oda is realising per year is gradually declining but let's just say that it stays the same from this point onward (2021)
36 x 5 = 180.
This is the basically the main reason why I can't believe the whole ''OP is ending in 5 years'' thing (which would be even less now). It would mean that Oda has to complete the Wano arc and do 3 additional sagas all within 180 chapters. I'd say it would be more along the lines of 7 or 8 years.
What do you think?