Well first of all Sigma confirmed again they are not developing an interchangeable mirrorless camera yet. Pity, would love to see a Sigma Foveon system camera.
On the lens front they will keep making APS-C or MFT lenses for mirrorless system but they have no plan to make lenses for the Sony Full Frame E-mount cameras.
Overall Sigma confirms that their main focus is still creating optics for the DSLR market. But I am pretty sure the day will come they will make more of those nice ART lenses for mirrorles systems including the superb 50mm ART.