Hi Jeremy, and welcome to the forum!
The relative scarcity of Pentax on store shelves is a problem that is often a subject of discussion here. Yours is a very valid concern. Purchase of a digital SLR seems to invariably mean the the eventual purchase of additional lenses and lenses are expensive. If your body wears out or breaks, it is good to know that you can simply buy a new one. Now if product is no longer available...
I personally can fill the fingers of both hands (and quite a few toes) listing off the camera brands that have disappeared during the 40 years I have been doing photography. Most of those brands live on in one form or another due to the activities of various collectors and cult enthusiasts who will continue to maintain and repair their film cameras as long as parts are available. Having said that, I sincerely doubt that there will be a cult forum in 2018 discussing the best way to repair/adjust the SR in a K20D. Complex auto-focus and digital cameras are fundamentally different than the film cameras of the past. They are consumer electronics and are not designed to operate for decades with minimal maintenance. To put it bluntly, except for the extreme high-end gear, most digital cameras are intended to be thrown away after 3-4 years.
One thing is good to know, Pentax has a strong parent company and has a market position as least as strong as the Sony, Panasonic, or Olympus digital photography lines. It also has a quality, high value product and probably has as good a chance of survival as many of its competitors.
As for your personal choice...much depends on what you are wanting from your camera. It is truly difficult to find product on today's market that is not excellent. It all comes down to what features you need, how much you have to spend, and most important, how the camera feels in your hands. From a hobby perspective, Pentax has a huge amount to offer. The easy backward compatibility to a wide range of lenses dating back 50+ years lends color and interest to the simple act of taking pictures.
Steve