Always nice with more FF players 
A lot of Pentax lenses are already FF compatible, so if it will be a success is mostly a question of price, and sensor noise/noise-cancelling.
I was deep into Pentax (had four bodies for quite a while, three of them digital) for cost reasons (originally), and the fact that the lenses were surprisingly small, & sharp; and I loved the fact that the excellent anti-shake system (SR) is built-in!
Old lenses work very well, as does many from other brands! The Menu system is the best I've come across, and the cameras are small(ish), and rugged.
When Pentax switched to CMOS they suddenly had problems with quite bad noise, even at base ISO, and the reds in images never looked natural. That is better now, but not on par with Nikon, yet.
A returned gift (my wife opted for the then new OM-D E-M5 instead), in the form of a V1, stopped my walk down the Pentax highway, and I have not looked back! I probably invested a bit over $20,000 in Pentax cameras, and lenses, and now I've invested a similar sum in Nikon gear. FX & CX, at the moment, sold the Nikon DX.
Couldn't be happier.
As museum pieces, I have one analog and one digital Pentax left, and a couple of lenses, that's all. The wife has a modern Pentax DSLR, and their snappy HD DA55-300 with the latest coatings, and that she only uses for BIF. Although that lens is screw drive the combo is one of the fastest target-acquiring system I've used, not a second of hesitation, for BIF excellent. The rest of her gear is Olympus, and Nikon 1 (two bodies, but only a 70-300CX lens, but I have a lot she can borrow).
