I seriously doubt OP was going to end in 5 years anyway, there are just too many unresolved plotlines, characters who need development or closure and uncovered mysteries left.
When you begin to even realize that the last 400 chapters or so has barely addressed any of the major plot points that have been set up in this series and Wano likely isn't even going to answer any of them save for a few hints lol. The Smile/Doflamingo/BM/Kaido plotline, while entirely necessary as they were teased characters pre-timeskip, it only resolves a minute portion of the entire plot still ongoing.
Made this list in another thread, and its not even fully comprehensive:
I. Characters
- Kaido's past/Rocks history/relationship with Big mom
- Remaining Rocks Pirates, if they are still alive
- Numbers, Yamato, the potential "Ace"
- Further exposition of BMs children at Wano (powers, personalities, etc)
- Vegapunk, his Special Science Group (SSG) and their goals, personalities, etc (I'm sure they are crazy as fuck)
- Kuma's goals, motivations, etc.
- Bonney and her relationship to Kuma
- Dragon's goals and personal motivations. Why did he not follow in Garp's footsteps. What was their fallout?
- Further characterization of the RA Commanders
- Reveals and personalities of CP-0 and its members
- Ryokugyu and his reveal
- Other Marine figures, formal introductions for Chaton/Momosagi. Other "Zodiac" Vice Admirals if they exist.
- Kong and his role in the World Government, other WG members. The hierarchy of the WG.
- History behind the Gorosei and their personalities, powers, goals, etc.
- Literally everything about Im
- Blackbeard, his end goals, full crew powers, personalities, history, and his 10th Titanic Captain.
- Shanks, his end goals, enigmatic personality, etc. His crews personalities, relationships, strengths.
- End goals for the Supernova
- Function/goals behind the Strawhat Fleet (their "major incident")
- End goals/plotlines from "Friendly" marines such as Koby, Smoker/Tashigi, Aokiji
- End goal/plotlines of every former Shichibukai (Buggy, Mihawk, Hancock, Weevil, Kuma)
- End goal/plotlines of every former villain (Crocodile, Enel, Lucci, Moria, Doflamingo, Katakuri) if they factor into the remaining story
- End goal/plotlines to extraneous characters/groups like the Underworld or the Level 6 Escapees still at large.
II. Locations (if we actually get them or just lore dumps)
- Nature of Pirate Island (Beehive) and it possibly giving some further background on Blackbeard, Davy Back Fights, possibly Underworld related. May or may not be significant in the end. We received the same kind of random introduction to WCI from FI about BM, its so its possible the Strawhats visit this location as a small/large arc.
- Vegapunk's Facility/Island/Emerald City (if we actually get to see it), it has been teased several times by Smoker, Fuji, etc.
- Elbaf and its gigantic tree has surely been teased. Hinted that it may have ties to sky islands, the moon, other islands, etc due to this tree and its size.
- God Valley and its significance to Rocks (and why Roger/Garp were also there at the time). Shanks being the same age as the incident is peculiar. Buggy possibly too.
- Lodestar being the last geographical island on Grand Line
- Laugh Tale being the final island in general and obvious reasons why we need to see it
- New Marineford/Mariejois as potential locations. Its very possible that the Final War takes place between these 2 locations and Fishman island for theorized reasons.
III. Plotlines
- How every notable faction mentioned either collides or concedes at the above locations or new locations. This includes how Luffy will surpass the 4 Yonko (+their end goals), fates of every character, significance of many others, etc. Wano's War, the Final War, etc.
- Plot relevance of King's (and Tengu's?) apparently extinct species
- The Last Road Poneglyph and its location
- How the Moon factors into the plot
- Origins of species/the world (the Moon lore sort of touches on this at least for the winged people with Enel)
- Origin/Nature of Devil Fruits
- Joy Boy, Rocks and Im, the 3 most enigmatic characters we have in the series we have thus far and their goals (dead or alive)
- Sunlight Tree Eve and FI's dependence on hiding under the sea (and its eventual destruction)
- The WG's National Treasure
- All 10 (for now) Strawhat dreams, EoS fates.
- Ancient Weapons and their usage
- One Piece
- True History