Supernatural's Eric Kripke has been working on TV series for Warner Bros based off of the popular Sandman comic, but unfortunately the show appears to be on hold. While talking with The Hollywood Reporter, Kripke said that "Unfortunately, for a lot of varying reasons, Sandman is not in the works, at least for this season".
There is no doubt that this is a difficult adaptation to tackle and has most likely been delayed for quality reasons. Kripke noted that he hopes to do the show sometime in the future, but there wasn't any other information on the reason for the delay or the plan for moving forward.
This is one of multiple Sandaman projects Warner Bros. has tried to get off the ground. There have been numerous attempts at a movie adaptation, as well as a cancelled TV project for HBO.