There are about 7 Bourne books - the latest is 'the bourne sanction' - which is good... so if that becomes a movie it will be good! let's hope for some more!
Paul Greengrass (director of supremacy and ultimatum) said he wouldn't come back for another movie and Matt Damon said he wouldn't come back if Paul Greengrass didn't come back. If they do another one it'll have a new actor play Jason Bourne which IMO no one can do it better than Damon. They have also said that they may do a prequel instead.
Very nice movie. I wonder if matt damon will be in the next franchise since their salary increases in every succeeding films.