I have finally gotten around to finishing this series after... I think it's four years! A kind reader emailed and asked when it would be done, and I suddenly remembered it's been sitting there half-finished and all unloved. So I've pulled up my sleeves and written it.
It needs to be edited and the rest of the series looked at for consistency, but it should be released in February next year. Sorry it took me so long to finish, everyone! When I'm ready, I'll put it up for pre-order at all the usual places and blog about it here.