I think Oda's statment is being taken too literally here. The journey absolutely ends when OP is found, but imo the story will still have its war/climax afterwards.
We know we have to return to FI at some point because Luffy/Joyboy is prophesied to destroy the island and Noah needs to be used to save FI. This suggests that the Final War probably takes place on Mariejois, because its directly above FI.
Laugh Tale "should" be beyond Lodestar, at least as we should be interpreting Inu and Roger's statements. Nobody can go beyond Lodestar. The Log poses stop working, which is why you need the 4 RPs after reaching that island.
Plus....Whitebeard mentions that finding One Piece leads to the war with the WG. Roger's statements after findinf it also imply the same thing, that using One Piece and the Ancient Weapons for "something" can only be done at the right time
I started to take all his statements too literally especially after "Luffy cant beat a strong guy like Kaido with a punch"...
If there is any doubt, there is no doubt. This scenario with Kuzan ending up the 10th is just another confirmation for it...
There will be a little story left after the treasure but I think only for the final biggest party in the world on Elbaf.
Everything else will be concluded before Raftel. I seriously doubt the WG war happening for at least 2 year with all secrets known...
The mystery has to remain until the very end so Raftel should come last. WG war will just give us some partial info and keep the mystery.
I dont think they will be goign back to FMI but who knows... If Raftel isnt in the New world, they might have to go through FMI again.
But as you said, it is more likely for it to be connnected to Mariejois due to location and the destruction happens during WG war.
Probably due an Ancient Weapon fired downwards, something powerful to tear through the Red Line all the way down to FMI.
Fishmen will likely be warned of this and Noah will be used for evacuation. Not sure how to tie it to Luffy being the one who destroys it...
Luffy usually doesnt need much to start a war with anyone, so finding OP first isnt really a must for him.
Capturing one of his friends is enough for him to go to war with them, we saw it in the Enies Lobby.
I suspect that Raftel is located right next to Crocus, beneath the Twin Capes.
There is already an X sign on top of it. It is submerged and thats why nobody can find it.
And Laboon hammering onto that spot could be another hint for it, other than hint for destruction fo Red Line.
The first part destroyed will be Mariejois/FMI spot and the 2nd part will be Twin Capes, probably during Luffy vs Blackbeard battle.
Gura no mi is fitting for the job...