You usually get to see pics of the next year production line in late January around the time of the SIA show. You might not get to see specifications of these products till much later in the year, often very late spring or early summer. Boards are "released for sale" usually in late August or early September. As far as when they go on "sale," -- usually they don't. NS does not overproduce their product line and sells their popular boards out by mid winter (Proto being one of those). You might find an odd size ProtoX for sale, but this "sale" won't be for much (?10% off).
My suggestion is to buy what you want while you can get it this year, but don't wait long. Proto's sold out by mid-season last year.