Just a brief reply as I'm still half asleep after a particularly impressive bout of insomnia, but Zandalor is certainly quite old as he was also in Original Sin: I forget the timeline offhand, but we're talking of the sort of magnitude of a millennium before DKS.
ISTR the suggestion is that further Divinity games would probably continue to use the D:OS engine and its successors, though I think it doesn't necessarily follow that all will be isometric so hopefully when D3 appears we might expect another third-person perspective.
I suspect that Larian is unlikely to "streamline" the various skills and attributes in future games: they seem to like keeping it interesting, in other words not overly automated!
And I think your knowledge of lore exceeds mine in both franchises: I spend most of my time running away from things and trying not to be pwned.
