I'm sure we're going to Elbaf, Laugh Tale and Mary Geoise. Other than that, we can go to Lodestar, Hachinsou, the moon, etc...
Ideally, Oda'll just address the remaining plot points in only three islands. I say ideally because I don't want him to unlive before finishing the story. And even just sticking to Elbaf - Laugh Tale - Mary Geoise Final War path will take around 10 more years lol