Personally, I'd rather see them (IGS):

1. Get to a good "stopping point" with current Valheim. Maybe the major Mistlands release and an update or two after?
2. Shift development to an Engine of their own, so they can break away from Unity.
3. Re-release Valheim in a better state overall using said Engine.

That being said, though, such a task could take years in and of itself. Porting what we have now to said Engine could take longer yet depending on the languages used, limitations of Unity that may have been coded around, etc.

However, this is assuming they can't use what they have already to get around the limitations the game currently has when it comes to things like altering the land. Personally I'd love to see the ability to generate cave systems within the world on world creation, the ability for the player to utilize/make their own caves, etc.

Plus.. an inner-earth biome where we fought the world serpent would be both relevant and pretty awesome. Would also give us a chance to see more of Haldor and/or his brethren, assuming they come from within the world itself.

But in a Greek mythos setting? We'd definitely see Gorgon, Bulls, Serpents of various descriptions, Basilisks maybe, Minotaur, Centaur? could be neat, although I'm personally more of a fan of Norse stuff.