I am definitely all for Day/Night Cycles and Dynamic Weather, I just highly doubt Larian will add them. Ultimately I get the feeling that their aim is not to create an immersive, open & dynamic world, but instead to tell a story and let the player influence parts of it. An area won't have a dark and stormy atmosphere unless it serves the story, the same for day/night.
I agree with those that say the lack of these features makes the world feel less alive, it makes things feel much more artificial.