This dpreview forum member claims that Sigma will announce their mirrorless interchangeable lens camera in few hours. Sigma has made a statement in the past that they are developing a mirrorless camera with a Foveon sensor. Based on the pictures, the new Sigma EVIL camera will have a M mount (Leica) unless there is an adapter. This could also be a DIY project, based on the existing Sigma DP1 camera.
Update: the original source of those pictures - this indeed is a DIY project initially posted on xitek.com.