Basically hearths are getting species-specific upgrades which also makes organizing who moves close to which hearth easier (so slightly more micro early game, but less late game in each stage).
Also some assorted stuff like new cornerstones and so on.
That’s great news! I stopped playing after the gold seal, but ill probably get back into it with these new features. I can only recommend the game for anyone who likes to play city builders with production lines, it’s such a refreshing take on the genre.