A little late to the conversation but I'll add my 3¢ anyway. I don't think lack of a FF body is the reason Pentax isn't 'popular'. Walk up to anyone you see using whatever the latest incarnation of the Canon Rebel is and ask why they didn't buy a full frame camera. Likely, you'll get one of 3 answers. 1: What is a full frame body? 2: Too big and heavy. 3: Too Expensive.
I would love to have a Pentax full 35mm frame body. In fact, I have several but their sensors are only good for about 36 shots at a time and I have to pay more money to see them. That, or play chemist.
It's been 3 years since I could walk into a store and put my hands on a Pentax dSLR. To say they aren't "Popular" however, is a misconception. How may other company subsidiaries do you see surviving with the lack of marketing and in store presence that HoyaTax has?