I have been very happy with the 18-135, despite the edge softness and CA at the longer focal lengths. So I'm in no rush to "upgrade". I use the 85-135 range quite a lot, and always carry the DA 15 if I need to go wider than 18, so the 18-135 is just about my perfect walkaround general purpose range.
My shorter term lens-buying priorities are projected more on two other lenses promised on the
lens roadmap: the "DA Wide Zoom" and the "High-magnification super-telephoto zoom". Both will surely take us into new territory.
Nevertheless, let's give the DA 16-85 a chance to show its wares. Especially if the IQ is superior, it will be an attractive option for many. Surely a useful addition to the Pentax lineup.