If they actually make 5 group mode work on pre 2012 cameras then I am in.
The Canon doesn't lose one stop of sync in radio mode, it is just an advisory, but if Yongnuo make it so that you get zero shutter shadow at closed down apertures with groups at full sync then they have smarter software engineers than Canon and if I were Canon I'd be headhunting them. You can probably employ five Chinese software engineers for one Japanese one and if they had access to the original source code they would be making far better cameras and accessories. If.
P.S. The RT system and my desire to get the best out of it is the single most compelling reason for me to upgrade my 1Ds MkIII's to, well I'm not sure what because Canon haven't given me an upgrade path yet..............
P.P.S. I don't know if the images are just a digital mock up but the Canon ST-E3-RT does not have the zoom control that is shown in the YN-E3-RT images, they might have used an LCD image from the flash, but if not they might be incorporating remote zoom into the YN-E3-RT as well, another useful feature for creative lighting.