I wonder what took them so long? I mean, it's not exactly rocket science... But they'll have to roll out a comprehensive lens lineup to complement that camera. The 70-200 and 150-450 cover the tele end nicely, but what about the rest? After all, in my perception the only USP of Pentax was the trio of "limited" lenses (31, 43, 77) but as time went by these were getting outdated and good new options were appearing (say, the Sigma 35 which is available in any mount). So what will they have to entice anyone apart from diehard enthusiasts?
That sums it nicely. They'll have to act fast and decisively on this one.
Well, it is rumored that Hoya would have never alloud to make FF, so we should thank to Ricoh. Another rumor is that Pentax will reveal new roadmap on CP+, and it will include quite a few FF lenses. Yet another rumor is, that Pentax had FF (24Mpx) some time ago, but when Canon 6D and Nikon D600 were announced, they decided to wait and redo what they had.
Concerning old lenses - FA 31mm, 43mm, 50mm f1.4 and 77mm are still in production, there is DFA 100mm macro, and in Japan one can get a new FA 20 - 35mm f/4. DA*55, DA 50mm f1.8, DA 70mm Ltd, DA*200 and DA*300 are usable on FF also (DA*55 and DFA 100mm macro were tested on Sony A7R, link is here, and look decent enough).
So, let's wait for Christmas.