Pentax FF will come but it's the price point that's the issue.
A $2,000 body and a slew of similarly expensive new FF glass is the barrier to volume sales.
Since the FF sensor and motherboard supporting electronics costs about as much as a K-500 total, there is no such thing as a "low-end" FF. All FF is immediately a very high-end product with just variable models in between.
FF will come when the sensors prices drop to where the original K-5 prices began. Over $1,000 body cameras will be FF (probably higher than US$1,200) and below that smaller sensors led by APS-C.
The bonus is you will eventually see $399 DSLR kits smaller and similarly featured as a K-50. That is how APS-C on the same k-mount (or Nikon, Canon, or Sony mounts) will compete with FF. Can you imagine taking the exact same photos as a K-5II in a body 1/4 the price? That's where consumers win.
And given that, will you be willing to spend 4x that for FF? And given that will you be willing to spend on that FF despite that fact 99% of your photos go onto Facebook or Flickr?
There is no getting around the pure economics of sensors that an FF version will be about 2.45x costlier than an APS-C version. APS-C files will be smaller and more in tune with the growing tablet era of computing power vs PC's which are non-existent in many markets.
People on this forum greatly over-exaggerate demand for camera systems over $1,000. for every FF sold here are something like 310 (non-smartphone) camera sold with smaller sensors. Price rules.
Here is the camera that Pentax needs to be concerned about
:
http://www.dpreview.com/reviews/canon-eos-100d-rebel-sl1/14
This is where sub-FF is going,and even smaller in the DSLR form factor. My prediction is that Pentax will need to put out smaller DSLR's (*ist size, even smaller than the K-x...and shed grams doing so) and merge the K-5/50 line, all with full specs. Entry-levelfeature leave-outs will decline (as the Korean auto makers are doing and thereby slaughtering their Japanese competitors) and we will see a more homogenized base. Video will be a very important selling point as will touch screens.