Originally posted by Pixel Walker:

I have the same question, I feel that the link above does not answer my understanding of the question.

To be clear, I think we want to know, come Myst release. Will we be able to keep our old worlds and evolve them into Myst or will we need to create a new world when the next expansion releases ?

I don't remember where I saw it, but the devs mentioned that you shouldn't have to start a new world. The world in Valheim exists in a strange sense, where only areas within 200 meters of you get created and set in stone. Meaning, if in your current world you have been within 200 meters of a Mistlands biome, it will have been created in its unfinished state and will never change from that. Any Mistlands biome you haven't been within 200 meters of, on the other hand, has not been fully generated yet and will be able to be explored once Mistland drops to the default branch.

You can probably check this by making a backup of your save, using the console map to reveal the map (I'm pretty sure one exists), and see if you have any Mistlands biome close to where you currently are. Do be sure to make backups though, and to replace the file with your backup once done. I've heard that using that method can set the biomes to count as explored, meaning they'll never populate with yet-to-be-released content.

Note: I'm not 100% sure it's a 200 meter range, but something like that.