No more so then Bat/Cat is, his exact words were, "I kind of wrote 26 pages of it, and it got shelved because the television work was taking up so much time,but again, I never say never because I think those 26 pages were pretty good."
I'm not holding my breath, but personally I'd put better odds on the Arkham sequel happening than Bat/Cat simply because Morrison and Burnham are thought of more positively and sell better than King