Your Promaster Pentax-mount lens will work with any modern Pentax DSLR*. Your older manual Pentax lens will too, but you will need to push a button to take a meter reading - they won't meter continuously. That's also the case with the XR Rikonon.
Some older Rikoh lenses are dangerous to use on Pentax DSLRs, but this one will be fine.
But, these are also not very high-end lenses. The kit lens you can get at low cost bundled with any new DSLR will be of much higher quality than your zoom, and probably of the two prime lenses too. Pentax made some great Takumar lenses, but the one you have is one of the lower-end options, and while it's fun, it's not great. And, finally, the Rikoh lens is generally well-regarded for what it is, but consider that it can be had for about $10 in the used market.
Pentax makes nice cameras, and they're worth considering as you look for a DSLR, but I wouldn't factor these lenses very heavily into that decision.
* Except the medium-format 645D range, which requires lenses with a bigger image circle anyway.