Sigma was expected to announce a new full-frame mirrorless L mount camera with its unique Foveon sensor later this month, but unfortunately, the company has announced that the camera will now be delayed indefinitely. Nonetheless, they still intend to release the camera eventually, albeit with a complete redesign.
Sigma's Foveon sensor works differently from a traditional Bayer sensor. A Bayer sensor captures the luminance of either red, green, or blue at each photosite, then interpolates the data to create the full image. On the other hand, the Foveon sensor takes advantage of the different penetrating powers of each wavelength by stacking three photodiodes into each site, each sensitive to one of the three primary colors. This means that each photosite measures full color information, and as such, Foveon sensors are generally known for producing impressively sharp images, albeit with poor ISO performance.
Unfortunately, Sigma has announced that they have delayed the production of the full-frame mirrorless Foveon camera indefinitely. Interestingly, however, the company intends to start again from scratch, redesigning the camera and devoting more research to the sensor technology. I certainly hope to see the camera reach the market eventually, as it is a very interesting device and would be a great alternative to more standard cameras.