UPDATE: Gematsu have also translated the interview.
UPDATE 2: It is possible that Tetsuya Nomura knows the release window, not the release date. This may have been from an inaccurate translation. Gematsu reports that he knows the release window and KH13 has reported that it is the release date.
ORIGINAL: During an interview with Japanese magazine Dengeki PlayStation, Kingdom Hearts and Final Fantasy 7 Remake director Tetsuya Nomura stated that there is a decided release date for Kingdom Hearts III that they cannot give at this time.
When talking about the release date, Nomura states in this translation by goldpanner, “We’ve reached an agreement, but I still can’t say anything.” He then said that “[he] plan[s] to give new information at the Kingdom Hearts Fan Event that will be held on the 3rd of November.” This fan event is referring to the D23 Expo Japan, which is a convention dedicated to Disney.
When asked about the development stage, Nomura said that “It’s moving along steadily. I’m currently deciding what to do about the ending and secret movies and such.” From these comments, there is room to speculate that the script and story are close to being finished for the game.
Kingdom Hearts 3 is currently in development for the PS4 and Xbox One.