Is it just me, as a reader, or should a book contain an identifiable story. Especially if you're going to cliffhanger the ending. To do otherwise disrespects me as a reader, and feels like you (or your publisher) isn't confident your series is good enough to get people to read subsequent books unless you resort to deceptive tricks.
Of course, maybe I should blame readers… because sometimes it seems like the obvious choice would be to publish a 1,500- or 2,000-page book instead of a trilogy of roughly 500-page books. But I suspect that ups the price enough to be counterproductive to sales.