My first reflex camera was a Pentax, the MX, manual mode and compact. A good classic camera with some professional qualities : Motor drive (5images/s) or motor winder, some 20 different focusing screens, a good automatic bellows and many lenses (40 and more)...Then came the LX, with his unique electronic and mechanic "hybrid shutter" (like 20 years after the FM3A or Leica M7 shutter)...but then came the FM2 and I bought one and changed for Nikon !
It would be sad if Pentax-Ricoh abandoned the K (KAF-2) bayonet but alas, Pentax has a very strange camera line, from DX to FX and MF (645D and Z) and with Canon, Nikon and Sony leading Full format and hybrid mirrorless cameras, Fuji and Hasselblad Mirrorless medium Format (Fuji also leading DX hybrid X-series)...where is the place for Pentax ?
That's probably why Sigma, but also Tamron don't make anymore K-bayonet lenses...(Tokina does, but not Tokina badged, rather Pentax, because of the Ricoh company proprietary of Pentax, Tokina and perhaps also Hoya ?)