UI is clearly work in progress, but I don't think general art direction will change, too much work for several months. So, we could more or less rely on it, but not the exact buttons, etc.
I don't like the unexplored area cover. Both CIv 5 and 6 looked better to me. Also, the overall dark UI is a bit depressing. But not a big problem, we'll get used to it really fast.