Since I was just thinking about it, here is a theory have about the latest and final release of the Jason Bourne films, The Bourne Ultimatum.  (And no, I have no affiliation with any part of the film industry, I haven't read any spoilers, etc.)

The Bourne Ultimatum is coming out on August 3, 2007 (very soon).  I for one cannot wait until it opens!  However, since I was just thinking about it, a theory about how it will all end just popped into my head. 

Regardless to how the books say this story will or will not end, we all know that the studios have the final say on such matters (once they purchase the rights).  While I was thinking about what happened in the first two, it is as obvious to me as it was with the ending of the Matrix trilogy... 

Jason Bourne must die.  He will never be happy unless he does.  However, knowing him, he will most certainly take quite a few people with him.  I could go into more detail why I think so, but it seems pretty obvious.  What does he have to live for?  There will likely be a mushy scene at the end where some semi-love interest doesn't want him to go, but he will.

As I said, this is my THEORY...  And as such, I am most likely dead-wrong.  :)  Forgive the pun...