According to egami, Sigma posted several new lens patents for APS-C cameras, these lenses are wide-angle zoom lenses, which is to be some new art lenses.
Sigma Wide-angle Zoom Lens Patents: 15-30mm F1.8, 17-35mm F1.8, 16-50mm F2.8, 12-24mm F2.8
Sigma 17-35mm f/1.8