Originally posted by chicagonyc Petaxovel is just paraphrasing Thom Hogan!
The counter to this is that Canon has a large, new fab that does not need to stitch FF, and Nikon is likely not far behind. That's a motivation to bring sensor development in-house. As with any other capital investment, the total outlay is recouped by BOTH the price per unit and the volume of unit sales. Canon now has incentive to drop FF prices. How far and when, we do not know. but if they get into the K-7 price territory, Pentax will not be able to make an APS-C flagship.
To keep putting out the next "whizzier designs" for FF or APS-C, it will require more capital for every technical advance. This doesn't change based on sensor size. Current Canikon FF users will want "whizzier" as well (du jour video).
At some point it will make more sense to consolidate manufacturing and design process into a single FF fab for as many models as possible, driving the FF sensor cost down as close to APS-C cost we currently experience.
This is precisely how APS-C got to be a commodity product, and FF will follow a similar cost: benefit curve. If an FF sensor can be made within $150 of APS-C, it will be 100% "satisfactory" for all users from flagship DSLR to mirrorless.
The "brighter" APS-C lenses is a silly idea. You already have that: DA 15/4 vs. DA14/2.8. Which one is the keeper and why? The amount trying to capitalize a two-tier lens system is likely proportional to the $$$ that could go to an FF fab instead.