I think that today, with WAR, his mini, the Immortal Men and even Outsiders, plus all his cameos, Duke has a lot of stuff to pick from to make an interesting mini/maxi-series or GNs. Also, I don't really want it but a writer could use Gotham-Girl (I hope it doesn't happen, but it could).
Hell, even Duke getting back his light powers could do for an interesting story involving his parents, Gnomon and the Arkham Juvie gang.