Raptorix01-- I understand that you (and lots of other people) would like to have Terry continue his works indefinitely. But, I think that he leaves all sorts of things apparently unfinished (Esk's son, Amber's future as Kelda, Laetia as witch, and I suppose even the certainty that Tiffany and Preston will marry--something Tiffany tries to ask her future self, but is only told to "listen").
The point is, these elements are useful to Terry in his primary focus in this book, which is the confirmation that Tiffany is a full-blown, competent witch around whom, as Granny says, her whole steading revolves. And, her defeat of the Cunning Man--who has been defeated once before (that we know of) by Granny should tell you that Terry probably has no intention of writing any more of the Tiffany books. This is the greatest test of Tiffany, the greatest threat to Disc world--and I don't think Terry thinks there's more to be said.
I think, as I've said earlier, that he's finishing off all the Disc world series (with
Snuff), and will write (perhaps with others for as long as he's able, other kinds of novels. I don't particularly like that conclusion, but I think it's accurate.