Piper, being the blatant Mary Sue that she is, is not a character I'd be too eager to see again.
As for the Kelvans, there is a SNW story involving them that I thought was hilarious.
John Coffren's "Gone Native" from SNW 9. In it, we see that Rojan and Kelinda and presumably the rest of the Kelvans from the episode are now living peaceful lives as farmers. A Kelvan prefect named Tamar arrives and harasses Rojan for not being a soldier anymore; Rojan turns Tamar into one of those little solid thingies and puts him in the barn.
