I would love to have a FF Pentax, but technically is the same to me to stay in pentax or jump ship. I mean, I have a partner, that shoots wedding with me, with a D7100. We are both planning to buy the new sigma 18-35 F1.8, because it "turn your apsc to full frame". In the other hand, Im buying a K3 with the lens (I have K30 and Kr atm) and not another D7100 as he would like me to do.
Middle-end of 2015, we are planning to sell all the gear and go FF with the savings of this wedding season plus some product and food works. If at that time Pentax had solved his lack of FF issue, I will go Pentax, if no, I will go Canikon.
The point is that it have the same cost to me, to go FF with Pentax, or go FF with Nikon, or Canon or Sony. Whatever I do, I have to buy some 24-70/70-200 f2.8 . Is a 5k investment, and at the momment I can do my work with a K3, a K30, a 18-35 F1.8, and a 18-70 F2.8. Maybe the little Tamron 70-300 that I called "Mr Chromatic Aberration" but I love nevertheles.
Sorry for my bad grammar, remember Im from Argentina