Well! That's what people originally thought actually happened on world changes. And then on one expedition, we found Paradisa Town, the site of a previous "world change". Since then it's been hypothesized that every time the world "changes", the characters are actually just sent to another location in the same world that for whatever reason is mocked up to be like something else. As for what we'll find, well, I have no idea so that's why it would be cool to check it out!