Don't forget Canon is a conservative brand, for lots of reasons, but one of them is that they serve as well a lot of working pros. Contrary to a popular belief, a lot of pros don't upgrade all the time with the latest and the best gimmicks all the time. They use what they have as far as it does the job, for money reasons, but also for ergonomics (muscle memory), habits and the fact that most of us need to know their equipment very well to make the best out of it and know its limits.
I just saw a 6 month old reportage where a fashion photographer was shooting a whole collection of swimsuits for a very fancy brand in St Barth, with a.... 5D3 and 24-70 f2.8 v1; that's the reality of pro equipment for a lot of people.
Lots of pros don't upgrade because they don't need to when their tools are good enough. So the TS-E line being part of the tools Canon designed for pros, I think it's unlikely they'll want to make them RF only any time soon, when EF TS-Es work exactly the same on both mounts. Yes we could see some optical improvements with short RF TS lenses (I guess we could call them TS-R), but what I am saying is that in real life for most pros, it will be more of a problem than a solution until the whole market has switched to mirroless.
The simple fact that I can finally use a convenient pol filter through the RS-EF adapter is a much bigger improvement than a slightly upgraded optical formula. Will my client notice a 10% increase in sharpness ? Absolutely not; but he will prefer 10 times that wood floor without glare and with better colors due to the pol filter.
I am very curious to see and certainly will buy a RF 12-35 f2.8L IS USM lens which was lately mentioned in Canon Rumers as in preparation. EF 11-24 f4 lens is a great lens in EF range though quite heavy. RF 12-35 f2.8L IS USM is the best alternative for RF series.I think the priority is in lenses not existing in the current EF lineup, or need an update, a 12-24 2.8 makes sense, as well a cheaper 50, but the trio zooms are still fresh with the latest updates
No 12-35, it’s a 15-35, it looks killer though.I am very curious to see and certainly will buy a RF 12-35 f2.8L IS USM lens which was lately mentioned in Canon Rumers as in preparation. EF 11-24 f4 lens is a great lens in EF range though quite heavy. RF 12-35 f2.8L IS USM is the best alternative for RF series.