Oda will wrap all the mysteries together within 2-3 chapters, I'm sure of it
How he would wrap it up:
Honestly, I think Oda wants us to stay on a never ending wild goose chase and never see the end of the "romantic mysteries" of the OP world/lore and because its much easier to write that way and safer too. Plus he can continue to milk us for decades like with Dragonball , Jojo, Naruto, Yugioh etc are doing.
The real Romance Dawn is the friends we made along the way.
"One Piece is not about the destination or treasure."