Director Paul Greengrass and Matt Damon are waiting on the next script. Before signing on to the fourth installment of the Bourne series. George Nolfi (Ocean's 13, Bourne Ultimatum) has been hired to develop an original script, since they won't be using sources from the Bourne novels. They instead will be using Robert Ludlum's "The Parsifal Mosaic" as inspiration for the next movie. The novel is not part of the Bourne series.
"deals with a U.S. spy who falls in love with another spy who is revealed to be a double agent just before her death. When he retires from the business, though, the spy learns that she may still be alive and sets out to learn the truth."