One question remains, why are they sticking with APS sized sensors?
Is their sensor design very expensive to implement in larger size?
Mostly due to costs. When the SD1 came out at $8000, that turned a lot of people off of Sigma. They will have to work hard to get that bad memory out of people's heads. The Dp series has changed a few minds, but ultimately are too niche for most.
That said, I've made flawless 20x30" prints from the DP2m and I know I can go larger.