It is still open, but it's on the back burner behind some fics I owe. I can tell you that one of the next stories I'm writing is Zuko's first experience with the Avatar state. Unfortunately, you don't get reactions, because no one, including Zuko, realizes what happened until years later. The equalist era will be very very different from canon, because Zuko will be an older, much more responsible avatar than Korra, and will actually have the wherewithal to deal with two massively abused brothers. Jet... is going to be fun.