Don't worry too much about lenses.
When Pentax releases a FF, the existing lenses on it will already make ppl stand up and take notice.
Why?
Smaller lenses than what competitors offer (not just the FA ltds, but most other lenses are smaller too)
The already nice rendering characteristics we see on APS-C in 135 format.
Think the smooth rendering and bokeh of the 31ltd but now on a wider FOV, thus accentuating the 3D look.
The raw sharpness of the 43ltd, used as a normal rather than a short telephoto 60mm equivalent that it is now.
77ltd, with its sharpness and 3D magic now, even better with the shorter working distance for the same FOV that we have become accustomed to on APS-C now.
Then there are the multitudes of legacy lenses as well as the already very good existing FA50/1.4; FA35/2; DFA50; DFA200/300.
So a Pentax FF will certainly offer something that other makes don't.
Just like APS-C now.
Yeah! babe.... I said the Pentax lenses on FF will make ppl look up