Personally -- recognizing that I'm in the minority vs. a lot of 24-longer folks out there -- I'd love to see a 24-50 f/variable IS USM and see just how small Canon could make it. I bet they could get that down to the size of the RF 35 Macro (perhaps a little bigger than that).
That may work for some. I think 70mm is about the shortest I’d be willing to accept on the long end for a walk around zoom lens. Here’s the dilemma: 24-105 is a better range, BUT there is a clear quality drop and increase in distortion at 24mm. In fact, the distortion on the EF 24-105 (version 1) is bad enough that I can’t shoot any kind of architecture with it - it is a wavy, unfixable type of distortion pattern. Instead, I opt for the 24-70 which still distorts good at 24mm, but in a correctable fashion. But then there’s the loss of reach, so for telephoto shots, have to consider a second lens.
The distortion on the RF version of the 24-105 looked very strong and noticeable to me - remains to be seen if it can be easily corrected like the 24-70.