I had my suspicions, but Scribner's wholesale cutting of the midlist caught me by surprise. It may have caught Scribner by surprise, too; it was Simon & Schuster that ordered the cuts. That "working on the next installment" is just a phrase that the publisher slotted into all its flap copy -- it was part of a template. Not intended to deceive, I'm sure, just something done during the rush of production.
It's a pity, because I had at least two more books in mind before I'd be ready to wind down the series. For one thing, I'd been building up to a showdown between Marian and Captain DiFalco, but now that will never be written.