--partner with a major camera manufacturer (ala - Fuji and Nikon)?
To reiterate a few things.
Fuji, Canon, Sony all make their own sensors. You can forget them right away.
Basically you have to sell to who is left, where it is mainly a foveon vs Sony game. And there are many issues and obstacles.
1: Nikon, Pentax are set on 1.5 crop. 1.7 would not be acceptable.
The big question in my mind, is why build yet another 1.7 crop sensor? Why disadvantage themselves like this?
Even if they built a 1.5 crop sensor, there is no guarantee anyone would bite. I don't think they have a compelling case.
2: I surmise sigma sensors are more expensive than Sonys for a few reasons. Economy of Scale, Penny pinching on 1.7 crop, and being fabless (profit must be taken at two stages for Foveon and for the Fab).
3: Sony has demonstrated ability to deliver large volumes and ramp new designs fairly quickly, and deliver chips that have faster datapaths etc. Foveon has not and represents a risk.
4: Foveon sensor may fail to meet all design targets. High ISO performance may still not be up to par. Off angle light may be more problematic (hence the 1.7 crop).
5: Possibly no competetive advantage is seen in the design.
While it generates Buzz for Sigma, Nikon and Pentax don't need that buzz so much and it the design is behind in any area, it could be more of a curiousity than a serious design.
Though a vocal minority see special quality the vast majority just don't care and see just a different set of tradeoffs.
Summary:
Basically I think that is it. I think they are not getting into any of the big guys unless they demonstrate massive success in the market elsewhere first. Like the Sigma SD14 outselling D200s. I think we all know that is not going to happen.
I think they failed to capitalize on their second chance, just as they did with their first. By delivering just 4.6 MP X3 in a 1.7 crop they will again be aiming for parity with entry level 10MP bayer cameras in image quality ( the way most people perceive it). Parity is not the way to win with a new design.
If you go by the green sensor parity in image quality as most do (essentially the 2X factor).
Consider that the original camera had:
3.4 MP green vs typical bayer with 3.0MP green. (Slightly more than typical bayer)
Now they have:
4.6MP green vs typical bayer with 5.0 MP green. (slightly less than typical bayer)
It should be clear that out of the blocks they will be in a similar competetive position as they were last time. Perhaps even slightly worse off. Consider that they are also no longer the hot new technology and they will not generate any more heat than they did last release. If anything they face many more DSLR competetors this time around. Sony A100, Pentax K10D, Canon 400d, 30d, Nikon D80, D200...
At minimum they should have delievered 1.5 crop 6MP X3 for this iteration to at least start ahead of the competition and to have the crop other potential customers might use.