Looks like this is gonna go ahead, Kubrick first started this project in 1969 but MGM dropped it due to the box office bomb that was Waterloo.
It's not going to be a movie, though; it's going to be a mini-TV series produced and directed by Steven Spielberg. Spielberg also handled another unrealized project by Stanley Kubrick which was: A.I. - Artificial Intelligence.
There is literally a behemoth of a book that covers Stanley's extensive work ethic in developing this film that would have been extraordinary: