Thanks so much for your thoughtful response. I'd differ with you on a few points.
Yes, a declining and mature market, but the DSLR market will increasingly tap into the camcorder and film market. People don't like to talk video, but there it is. When I talk to my kids about a photographer who just takes stills, they think it's the dumbest thing they ever heard. To them, the first choice is "picture or video?" Also, the lag here is increasingly the hardware of the computers, not the cameras: 4k video is well within the range of filmmakers—it's the edit hardware that's prohibitive.
Entry level people aren't more likely to start APS-C. Not when there are full frame entry-level cameras. When full frame reaches that market segment (and by then the cameras will be the same size as APS-C cameras), APS-C will be well on its way to obsolescence. But, FF may not reach that market for a few years. Enthusiast market? By the end of this year (look at the Sony and Canon offerings), it's going to be very difficult to sell a new APS-C camera to an enthusiast. Pentax has to diversify into FF. Committing fully to APS-C at this time is poorly advised. (And the K mount is an ff mount, with FA lenses that can be updated in the short term.)
Current FF people aren't going to switch gear. More or less that's true. But people upgrading from APS-C, and there will be a lot of those in the next few years, will be open to the possibility. They need new lenses anyway. It's also been my experience that Canon folks don't love their lenses. On the video side, many Canon shooters rent lenses.
I do love my Pentax lenses, as do, by the way, my Canon buddies, who are using them with adapters. It bums me out to think of leaving Pentax, and the upgrade path from my K3 is prohibitive. To get the control I have in the K3, I'll have to drop 3-4 grand on, for example, a Canon. Maybe I could spend less on the forthcoming Sony A99 updated camera (the A99 is an obvious model for Pentax, by the way, because it allows for the APS-C crop factor, and APS-C lenses).
Anyway, I'm the market, I think. I came in entry-level with Pentax a few years ago, then upgraded (pre-ordered) to the K3, which is a beast, and now I'm planning to move up again—and the move, seems pretty obvious, is FF. Basically, I want to get the aperture values of ff lenses (without the APS-C crop). I'll watch what comes out until the end of the year, and if Pentax isn't there, I'm going to Canon or Sony. I'm not fond of Sony, but the sensors are Sony, and at least the A mount has a history.
Oh, and by the way, I've spent quite a bit of money on Pentax, but the lack of FF has put a moratorium on that. I'm wait and see now. And I'm not the only one. I don't know if any company can afford that kind of bleed.
