The discussion should perhaps be about whether Pentax
should release a full-frame DSLR, not
if or
when they are going to. The "if" or "when" question is more suited to the news and rumours section.
For marketing reasons, I suspect Pentax will be forced into a full-frame, assuming that the current trend among other manufacturers is successful, or they will risk becoming something of an irrelevancy in the market segment they currently occupy.
I realise there is an element of having to "keep up with the Joneses" in this argument, but I think it's also fairly clear that sales success with the main product line of just about anything that's sold these days depends to a great extent on having a high-end product that provides the rest of the line with buyer credibility.
While it's a bit irksome to engineers like me, it's also a fact of life that marketing decisions about products are based in fairly well-established notions of human behaviour, and it's no good having the best product in the world if it fails to capture the buyers' imagination (or, you could say, lack of it) and their pockets.
There are, of course, a number of manufacturing economics factors involved here as well. While developing a new camera (even one, perhaps, based on the existing range to whatever extent is practical and necessary for pricing reasons) is one thing, having a matching range of lenses and accessories is quite another. Fortunately, there are still some full-frame lenses available and presumably being made in small numbers, and the designs for the rest are still extant. Tweaking them for the required automation systems is probably more of an effort than starting up the optics manufacture again, of course.
Speculation is interesting and all very well for an interested outsider, but my view is that, if the top people in Pentax aren't thinking along these lines and doing their sums before deciding one way or another, then there's no hope for the marque in future, full-frame or no full-frame.