I bought a fisheye lens around 10 years ago. It was a good quality but cheap 3rd party lens. The next day I went out and had a lot of fun with it. After that I put it on a shelf and it has sat there unused since. That tends to be the life history of fisheye lenses.
The Canon 7-14mm might be a technical marvel, but I can't see spending big money on a lens like that.
I wonder if this will affect the used price of the EF 8-15 mm fisheye. Just this week I considered getting one of those for about 1/3 of the price of the RF version. Even at that price, I thought I could do better for a lens that will get limited use. I've owned a couple of circular fisheyes and they're really fun and challenging to use, but it's not a lens with a place in the regular rotation. I don't think I'll be spending $2K for the latest and greatest.