The next GM lens from Sony will be FE 16-35mm f/2.8 GM lens, a wide-angle zoom GM lens from Sony.
Sony has already released three GM lenses: FE 24-70mm f/2.8 GM, FE 85mm f/1.4 GM, and FE 70-200mm f/2.8 GM (Currently still out of stock). So the next GM lens will be Sony FE 16-35mm f/2.8 GM lens. SAR said this lens has already developed by Sony.
via: SAR