Technically - they could develop an algorithm to update world for new version. Seed is just sequence used in generation algorithm. Technically they could make an algorithm - that scans existing player assets in existing world, then generates new world of the same seed and transfers player assets over. After all, the world depends not only on your seed, but also on generation algorithm. If they change algorithm for existing biomes - you would get two different worlds with the same seed.

Fact that devs didn't address this yet makes believe the don't plan on any compatibility "regenerating world" for future updates. That just terrible approach for such an expansive world. By time final biome drops - most people will have no will left to go over thru everything yet again. Looking from another angle - why bother when you already sold like 10M copies?