There's a good article on cnn.com about Matt Damon and Bourne Ultimatum
http://www.cnn.com/2007/SHOWBIZ/Movies/08/06/matt.damon.ap/index.html
"Damon said he senses he's done with the "Bourne" films, but he might be interested if Greengrass were to return to make another.
Greengrass and Damon hope to collaborate on the Iraq war drama "Imperial Life in the Emerald City," though Damon may be unable because of a scheduling conflict for Soderbergh's upcoming corporate-whistleblower tale "The Informant."
"Ludlum's "Bourne" books were set amid the Cold War, but Damon said the movie adaptations reflect our current world. Though the Iraq war is not explicitly mentioned, Bourne's actions and revelations serve as a commentary on those events, he said.
"I just love that he tries to atone for what he's done at the end of the second movie. It was a really nice thing in a kind of mainstream action movie. To have that be your final beat is something I had never seen before, and I liked what that said particularly at that time," Damon said.
"All of these movies are very much of the time that they were made, and at a time when we had gone into this war. To have this character aware of what he had done and try to take responsibility for his actions I thought was a really good thing."
And how is "Bourne Ultimatum" of its time?
"It's this guy who has done these horrible things, but now we see he thought he was doing them for the right reasons at the time he did them, but he realizes he was sold a bill of goods," Damon said. "So that's very much a movie for today."