It will apparently deal with multiple stories all taking place in and around Hollywood in that year.
While originally Quentin Tarantino’s film was reported to deal specifically with the Manson Family murders, it has now been clarified that the movie is actually about 1969 in a much broader sense.
With word from Deadline that Margot Robbie is still considering taking the role as Sharon Tate, it would seem that the Manson situation will be part of the film, but it appears to be just one story of many that might not have any more weight than the one that Leonardo DiCaprio is part of.