The Paul Dini Zatanna/Black Canary graphic novel is sort of "in development" in the sense that it may eventually happen.
From a recent interview with Didio on Newsarama, a Zatanna ongoing written by Dini is already well underway and they are just letting the SECRET ARTIST get enough issues under his/her belt in order to keep it coming out regularly. Sort of like Batwoman-turned-Detective Comics.