Originally Posted by turtle
The blending of chunks also makes it seem like a same bet. I haven't seen a "before and after" but in the Minecraft Live video there were some tame examples. I'm not sure how far off it would be if there was an ocean chunk next to a mountain biome. It will be interesting to see how it handles the smoothing. My guess is the smoothing is in all the new chunks leaving the old chunks as they were so they don't wipe a portion of your existing build.
The wiki says this:
Upgrading of old worlds
- Terrain from new chunks will now blend with existing terrain from old chunks. Any player-made structures in these chunks will be either intact, buried, or deteriorated.
- The old bedrock layer between Y=0 and Y=4 in old chunks gets replaced with deepslate.
- If there is bedrock at Y=0, lower places in old chunks will be filled with deepslate and caves.
- A new bedrock layer is placed at Y=-64.
Sooo.... ¯\_(ツ)_/¯ Worth a test as we get closer to release date.
I'll leave it to you guys to decide on the upgrade path, whether it be new Overworld or upgraded one. I've been spinning the random seed generator in Chunk Base and found an especially nice one with many 'rare' biomes within 1K blocks of spawn, so if we go with a new Overworld I'll put that seed up for consideration.