From SciFi Wire:

The Jim Henson Co. announced that it will produce a feature-film sequel to its 1982 fantasy film The Dark Crystal, with the working title The Power of the Dark Crystal.
The original movie was directed by Jim Henson and Frank Oz, with conceptual designer Brian Froud, and has remained a fan favorite with consistently strong worldwide home video and DVD sales, the company

The company’s co-chief executives, Brian Henson and Lisa Henson, made the announcement. Odyssey Entertainment will represent the worldwide sales and distribution of the film, beginning immediately at
the Cannes Film Festival.

The sequel is based on an original screenplay by Annette Duffy and David Odell, who wrote the first film. It is set many years after the events of the first movie. The Power of the Dark Crystal
sees Jen and Kira as king and queen and guardians of the crystal, who fight to save their kingdom when the crystal is once again split. Incorporating a hybrid of live-action animatronic characters and computer animation, the production is expected to commence in the fall. Lisa Henson and Kristine Belson will produce, with Brian Henson, Ralph Kamp and Louise Goodsill serving as executive producers.