The Canon RF lens lineup is growing nicely, though there is still a hole at the ultra-wide angle end of the lineup. Thankfully, however, that will likely change soon, with a premium ultra-wide angle lens on the way.
Canon Rumors is reporting that Canon is planning to release an ultra-wide lens in the first half of this year. Though there is the RF 15-35mm f/2.8 L IS USM, lenses with significantly wider focal lengths have increased in popularity in the last few years, and I suspect Canon wants to follow up on the EF 11-24mm f/4L with an RF version of some sort. I was a big fan of the original EF 11-24mm f/4L in my review, and I suspect a new version would be popular, particularly with landscape and architectural photographers. Recently, three patents emerged for just such a lens: an RF 10-24mm f/4, RF 9-18mm f/4, and an RF 11-24mm f/4. If I had to guess, I would suspect the 10-24mm f/4 is the most likely to come to market. Canon has shown they like to extend the capabilities of RF lenses a bit beyond their EF counterparts, and this specific design has been rumored for several years. Hopefully, we will hear more news soon!
If it is as good as or better than EF it will be the lens to have for anyone wanting a superb wide angle lens only available from Canon.