I think the problem was that being one of the oldest books and being left for.last gave seraphon players (me included) an expectation of a large release, maybe with updated models that we desperately need (plastic slann?). Now given the lack of more news it seems it may be just the terrain piece, making us a bit disappointed, so.we just want the book..
The old book didnt hold up at all, our lore is almost inexistent so we are never mentioned in stories, our warscrolls have suffered a lot from power creep and the meta changing to mortal wounds. What saved us mechanically was the summoning introduced in the GHB + teleporting with skinks. Meanwhile all the saurus units (3 battlelines) gather dust due to being unusable.
We just want the book to inject new lizard goodness into aos, and make half of our units viable again.