Night Kingdom was a very real project Disney was doing and it was was definitely way past Blue Sky. I know I have zero credibility here since I am only a lurker but I, along with about 10 others, was once given a presentation by Disney on the Night Kingdom concept. I can go into all the details but essentially under the Breezeway next to Innoventions East I was approached by a Disney Researcher cast member who asked me a few general questions. Upon the end of the questionnaire I was given the option to do a further research opportunity and to compensate me the researcher gave my family FastPasses to a few rides. I said yes and they told me to report at the same location a few hours later. Upon doing so I showed up amongst around 10 others and they took us into the Wonders of Life pavilion and into the offices. They made us sign a non-disclosure letter and told us that the room was under surveillance and microphone for research purposes only. Two cast members, who I assumed were Imagineers, proceeded to tell us the concept of Night Kingdom. They had many, many pictures and a video as well showing us the concept. The park icon was supposed to be the moon. The park was centered around experiencing different cultures as well as doing different activities like zip lining. They wanted a few different "treks" - one I remember was the cultural one where you had dinner and partook in the nighttime activities from native people of a different culture. Another was a more adventurous trek where you zip lined, went on a nighttime safari, among other things.
Obviously the concept may be changed by the time more people started to become more aware of it before it was eventually scraped but I just want to let you know that it was a very real, very detailed concept that was presented to me and that Night Kingdom is not some made up Jim Hill concept.