We were told almost immediately after the announcement of the EF 16-35 f/4L IS that Canon is indeed working on an f/2.8 ultra wide angle zoom. The lens will be wider than 16mm, although the exact optical formula is not known. We have heard in the past that an EF 12-24 f/2.8L or EF 14-24 f/2.8L was in the works to compete with the Nikon 14-24 f/2.8G, which some Canon shooters have converted to their EOS bodies.
It was stressed that the lens was “not close” to being announced, and would probably arrive within 6 months of a higher megapixel full frame prosumer camera body.
We're also told that the Canon EF 17-40 f/4L will remain a current product in the Canon lineup for the time being. Although with how close they are in price, which I'm still surprised about. I can't see many people not savings a bit longer for the new lens. This may be a matter of depleting stock before discontinuation.