Frankly I don't see them getting much concrete inspiration from Dark Souls. The game takes a very minimalistic, show-not-tell approach to narration and mood-setting. A dialogue & story-driven game is almost the antithesis of that.
Oh, there's a lot they can take. The best inspiration they could take is to make everything click with itself. Game mechanics, lore, level design, encounter design, music, atmosphere, architecture, etc.: the Souls games do it with such perfect feng shui that it is nothing but admirable. That's something that can and should be taken by everyone. Every aspect of the game needs to work and enhance each other, like one big machine. The anti of this would be the boss encounters in DE:HR. Developed by a different company who obviously didn't know what the main game was going to be like. They feel completely out of place from the rest of the game and shit on pretty much the whole design that the game was building on up until that point.