Where do the sky islands come into the future of One Piece?

[Warmmedown]

We know there are more sky islands, because Gan Fall mentioned another way to reach Skypeia from the West or something (look it up). He knew the SHs were non-sky people, so it must be from land. That other way is supposed to be a less dangerous way to reach the sky islands. So maybe a sky island is reachable from the ground. It could be that they're reachable from the Red Line, where the Celestials live. The Skypeians, including the ancestors of Squire Gan Fall, have been separated from the ground level for 100s of years. So they may not know the Red Line is now inaccessible for non-Celestial Dragons, as it's a more recent development (they may not know it was via the Red Line that groundfolk visited the sky. They just know people came from that direction, but they don't know things like "Red Line"). Previously anyone had the right to visit the Red Line or maybe many people lived on it, but not any more. Skypeians have heard that people can go to the other sky islands from the ground over there, so Gan Fall assumed the SHs came from there too. Or maybe it was only CDs who visited via the RL and Gan Fall thought the SHs were the same as the Celestial Dragons (because he's not familiar with groundfolk politics).

Maybe all the CDs plan to move to the Sky Islands and then launch to the moon. That's where their launchpad is.