I bought the ef 8-15mm L fisheye as soon as it was available and it's a really fun lens that is suprisingly versatile. However it needs judicious use in a collection of photographs. It's ability to cover fully circular 8mm and full recilinear 15mm fisheye views is unique. It's very small and light...and with a ef-rf drop in filter adapter...I can use ND filters with it.
I personally can't see what a RF version can bring to the table except that it gives Canon permission to kill off the old ef version in 5 years or so.
There are a few niche ef lenses that really do need a warm over. These will never see the light of day as mk II ef lenses...so my only hope is that thye will be RF lenses instead. The ef 180mm f3.5 L macro is another of those niche lenses. It's far better than any other variant of it's type from any other brand. It's not until you try the Sigma, Nikon, tamron etc until you realise how good the Canon variant is in comparision. But it could do with newer optics, coatings, AF motors and yes...a modern macro capabile IS system. However, the EF version is so niche it still commands a high price...I shudder to think what Canon would charge for an RF version!
If canon were smart with their TSE-RF lenses, they would include a rear drop in filter slot. That would level the "features" playing field between ef and rf variants.
I like the idea of a super wide f1.2 prime lens. Looking at the block chart...that's got some seriously funky glass shapes in there...that isn't going to be cheap or light weight!
