@Paperchampion23 What if Sphinx is the next island instead of Lodestar? If Luffy vs Sakazuki is to happen, that’d be a good setting for it
Oda doesnt have the crew visit Islands we've seen already in its entirety. This is why things like Pirate Island, Banaro, Sphinx, Winner, Raijin, God Valley, Baltigo, etc dont happen because he uses those settings for other characters.
Imo, Sakazuki has his role to play against he other Yonko when the Burned Scar Man gets involved. This is because Blackbeard has Garp (which means Sengoku and Tsuru wont sit still), and Koby has explicitly stated he wont let Luffy become PK, which means the Marines need to be involved beforehand. Not only this but Ryokugyuu intends on fighting the RHP eventually, Kuzan's plot probably is Marine related (i.e. Smoker/Sakauzki) given he captured Garp, and you have the fact that Cross Guild is putting bounties on Marines.
Personal headcanon is 3 Islands left, plus a final WG conflict:
- Island after Elbaph: BSM setup and who they are/where they will be. The Grand Fleet meets back up with Luffy. Luffy finally meets Shanks, etc. Not sure when or how Teach gets Pluton or Poseidon, but I assume this happens soon. CG get the remaining former Shichibukai (Doffy, Moria, Weevil, possibly Hancock) to join them at this time.
- Lodestar: Is where all 4 Yonko and Marines will fight over the right to go after One Piece. Big Mom's crew try to save Pudding and fail. Perhaps Shanks and Sakazuki lose here along with their groups, and get good endings. Blackbeard and Luffy get copies of the 4th RP and race to LT. This is the "great incident" that the Straw Hat Fleet takes part in, since the Marine force and Yonko system basically is destroyed after this.
- Laugh Tale: Void Century, BBP vs SHP over One Piece. PK status
- Mariejoa/War: Fight against the WG with all allies (Good Marines like Koby and his Sword group, Supernova, Fleet, Loki, Yamato, Momo, Vivi, Kyros/Rebecca, Neptune, Shirahoshi, etc), plus the RA.
Thats how I see it but who knows how any of this plays out in the end.