I found this at wikipedia.org
George Lucas began writing the new Star Wars trilogy on November 1, 1994.[2] The screenplay for The Phantom Menace was adapted from Lucas’ 15-page outline that was written in 1976. The early outline was originally designed to help Lucas track the character backstories and what events had taken place before the original trilogy.[2] While the working title for the film was The Beginning,[2] Lucas later revealed the true title to be The Phantom Menace; a title which, in contrast to the more self-explanatory titles of the other films, is ambiguous
He didnt have the saga planned since 1976 did he ?