Do some searching to see if the older Pentax gear will fit the new dSLR. If they are anything like Canon and Nikon the old lenses will mount on the new digital bodies. Depending on the class of lens (at least with Nikon anyways) different features will be usable on the new bodies.
Basically the older the lens the less options are available due to the lack of electronics on the lens itself. You can mount some OLD lenses on Nikon, however they are manual focus and aperture only.