Disney is making a sequel to the Dark Crystal. The title is The Power of the Dark Crystal. Here's a little bit about it from the Cinescape website in an article about composer Trevor Jones:
After that, Jones will return to the milieu in which he gained his first major notoriety, with the score to Brian Hensenís THE POWER OF THE DARK CRYSTAL, a sequel to the laudable 1982 fantasy that featured The Henson Companyís magnificent life-size puppetry. The film, which is scheduled to be released in 2007 by Disney, depicts Jen and Kira as king and queen fighting to save their kingdom when the crystal is once again split.