Sigma: We will not make any mirrorless system camera.

The new Sigma 30mm on the NEX-7. Image courtesy Mike Kobal

A Sigma Manager stated in an interview at Xitek (Translation here) that they will never launch an own mirrorless system. But they will do lenses for other mirrorless systems instead.

P.S.: Links to the first Sigma mirrorless lenses:
The 30mm lens is in Stock at Amazon US (Click here), Amazon DE (Click here), Amazon UK (Click here), Amazon FR (Click here), Amazon JP (Click here) and Digitalrev (Click here).
The 19mm lens is in Stock at Amazon US (Click here), Amazon DE (Click here), Amazon UK (Click here), Amazon FR (Click here), Amazon JP (Click here) and Digitalrev (Click here).