Not possible enough for Canon's marketing dept. to be able to pitch such a huge heavy expensive thing. If we're talking FF then f/2.8 is the max practical aperture for an ultrawide zoom.
But something closer would be forseeable: a ~18mm wide angle with a very large aperture. For the EOS M system.
EOS M's flange focal distance
is 18mm, so anything this wide or longer doesn't need to be a retrofocus design. I would go so far as to suggest that the ~18mm distance of APS-C mirrorless systems was specifically selected because
they wanted the FF equiv of a 28mm wide angle without requiring retrofocus lens designs.
This is why Fuji's XF
35mm f/1.4 is small & light & costs 500 bucks, and their 18mm f/2 is a pancake. They've got a stabilized 18-55 f/2.8-4 standard zoom the size of the EF-S 18-55 kit zoom as well.