Whilst Matt Damon, Greengrass, even the studio said that "The Bourne Ultimatum" would be the last film of the series, Damon himself seems to have changed his mind during interviews this month for the release of "Ocean's Thirteen" in Japan.

"Personally, the character means a lot to me because the character has done so much for my career. You know, it put me in the position where I have a lot more choices of kind of movies I want to make".

"If ['The Bourne Supremacy' and 'The Bourne Ultimatum' director] Paul Greengrass, maybe years down the road, was interested in doing another one, then I would do it, too. I don't think either of us completely put the character to bed yet."

It would seem likely that the fourth book's title "The Bourne Legacy" would also be employed.