I'm hoping Henson Co. will ditch Power of the Dark Crystal and start fresh -- greenlighting a prequel movie.
It really would be campy to have a sequel where the urSkeks come to Thra again just to check how things are going. "Hey guys, just stopping by to see how the Crystal of Truth is..."
Then the Crystal cracks again...
A prequel movie (or movies) is the way to go. You can have a totally new story and you can have your cake (The Crystal's cracked, the Gelfling race is back, the Skeksis and Mystics are still on Thra) and eat it too.
I'm crossing my fingers hoping that this YA novel series will be a way to round up the fans back to the Dark Crystal -- get them interested again -- plus get some new fans along the way, before beginning production of a prequel/sequel movie.