The going rate for the non-OS version of this lens is between 28,800 yen and 35,000 yen in Japan for all mounts, and has been for the past six months or so. It still seems to be available at most retailers, but I've seen places that no longer have it in Pentax mount. I remember reading speculation that Sigma was trying to get rid of stock of this lens and some others to release a successor that doesn't infringe on Nikon's patents (although the Pentax version omits OS, which is what the infringement was concerned with).
Sigma ordered to pay $14.5 million in compensation to Nikon for lens stabilization patent infringement
I'm tempted to get one while it's still available even though it's too big to be comfortable on my current body (K-01). If a successor comes out, it is bound to be more expensive and how long the wait would be for it to come out in Pentax mount is anyone's guess.