A lot of important things have been revealed in this arc so far. First, we learn what family Sanji is from and now we learn more about the poneglyphs, who made them, and how they can lead to Raftel.
Now that we know why the Beasts Pirates were after Raizo and the samurais, I’m pretty sure that sometime in the future, we are going to see a heartbreaking flashback concerning Kozuki Oden. And when Luffy meets Sanji again, we are going to learn more about the Vinsmoke Family and why Sanji ran away from them.
So what’s going to happen next? Luffy’s rescue operation or another head-to-head confrontation with the Beasts Pirates (Sanji’s group had one right after arriving at Zou).
As for the confrontation between Kaido and Kid’s alliance and the battle between the Blackbeard Pirates and the Revolutionaries, it is likely that those events will happen off-panel during the present (like Jack’s attack on Doflamingo’s Marine escort) and the outcome will either be mentioned later on or be shown in small flashbacks during future story arcs.
Here is a list of things that need to be seen before the series end:
- the appearance of Vegapunk and the technology he used to combine Devil Fruits into inanimate objects
- what the Blackbeard Pirates used to absorb Devil Fruit powers
- the appearance of the snakeneck tribe (first mentioned on the list of slave prices)
- the appearance of Pluton
- the last ancient weapon, Uranus
- the national treasure of Mariejois
- the upcoming reverie first mentioned during the Fishman Island Arc
- Luffy’s mother, Dragon’s backstory, and the forming of the revolutionary army
- the full history of the World Government’s origins and the ancient kingdom
- the full extent of the Gorosei’s power (other than political power)
- how Lucci and his comrades came to be working for the World Government again
- Noah fulfilling its purpose
- the identity of Joy Boy
- how and why Luffy would destroy Fishman Island
- the information on the poneglyph Jinbe discovered during his cover story
- the location of the fourth Road Poneglyph
- the All Blue
- what’s on the Rio Poneglyph
- what the initial D. stands for
- what is One Piece