Xebec is locked in Impel Down, frozen. Might be his clone.
But I have no idea when that black ship thing happened.
If he works for WG, the RPG can end up on the Red Line.
That would make WG war just a warm-up for the PK race.
Which fits with Oda's statement that OP ends when treasure is found.
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