It's a shame, but Spurrier's Legion story has had no real follow-up, despite a decent amount of use for David these days.
Oh, also: for those intrigued by the "cloning" going on here, I highly recommend Last Days of an Immortal, an absolutely beautiful and compelling graphic novel. One of the best things I've ever read, and it illustrates some interesting notions about cloning, among other things.
-Pav, who has read quite a lot...