I think the wide end for RF-S is the most needed lens - a 10-22 or even something like a 9-20, similar to the M lens would be welcome.
Also, as mentioned, a 15-xx, maybe even a constant f/4 lens, would be welcome as a higher-end "normal" zoom. And, of course, a couple of lightweight, fast primes like that 32 f/1.4 and the 22 f/2 in the M format.
Of course, there are some needs on the full frame side as well. The proverbial 24/1.4 and 35/1.2 are needed and have been rumored forever. A longer macro lens, and the aforementioned super tele zoom (200-500 f/4), but there ought to be something that competes head-on with Nikon and the Sigma/Tamron telephoto zooms. Although the EF version of the Sigma 150-600 doesn't play well with eye autofocus on the RF mount, I think that the situation will change at some point, and Canon ought to be ahead of that game.
I'm not sure of the need for an RF-s superzoom. I mean, slap that 100-400 f/8 on there. There wouldn't be a lot of weight savings on longer lenses by going to the crop format. Most of that size improvement comes at the wide to midrange end of the focal length.