Though Bishan has never been seen, and not referred to very much, he still remains a significant part in Farscape.
Overthrowing his cousin Rygel, Bishan caused Rygel's incarceration by the Peacekeepers, possibly hiring them for help in this. Rygel looks forward to the day he can return to Hyneria and overthrow his cousin.
However, this wouldn't be so simple, as D'Argo commented that those Rygel trusted on Hyneria to help him would be on Bishan's side. Even so, Rygel states that it is his destiny to wrest his throne from his cousin, and so Bishan could be a significant character in the future.