Tony Gilroy, the screenwriter for the original Bourne trilogy, has signed on to write the treatment for The Bourne Legacy, the planned fourth installment of the franchise. Gilroy joins Frank Marshall and Pat Crowley, who have returned to produce.Despite the positive momentum, not all of the original pieces are in place. Actor Matt Damon and director Paul Greengrass have yet to sign on to the project, and Damon has stated that he will only participate if Greengrass directs. Then again, people say a lot of things. My old girlfriend said we'd be together forever, but as soon as she got the starring role in Precious, she dropped me like an empty Taco Bell wrapper. Be careful, Greengrass. It could happen to you! (Deadline)