Originally posted by Steve Beswick True, but the A series lenses still worked as well as M series lenses. It's not like you were reduced to stop down metering or something comparable.
Just to provide something comparable... MZ-S owners also lost the ability to control aperture with Av mode when pentax released DFA 100 WR and possibly all future DFAs, even though that lens is supposed to be compatible.
The point is: IMHO Cameras are for the most part not made to be forward compatible, be it loss of AF, aperture control, or anything in between. The camera was advertised to be able to do certain things when it was released, and it's not like pentax released a mandatory firmware downgrade so that it stopped doing that (unlike sony and playstation 3). And there's a wealth of screwdrive lenses to choose from. If one has the money for future DC / SDM only lenses, it is likely that he or she would also have enough for a K100Ds / K10 / K200.