Will be over 3Kg, too heavy for me.
Shame, as they probably could have got a Mark III 500mm prime down to 2.4Kg. That's just about hand-holdable for me.
I suspect that Canon have an "internal eyes only" lens road map that has been working a long game. I suspect that the RF lenses were on this road map and were influencing the EF linage long before any of us were even aware of the RF developement. I think the secrecy of this road map was essential back then but less so now. The fact that the EF 70-200 f2.8 mkIII was just a coatings update to the MkII...making way for the innotave RF version (all of these features could easily have been made on the EF mount. The fact that Canon never addresses the EF 50mm f1.2 L replacement...but bought out it's effective answer in the RF mount are just two examples.
The fact that there wasn't a ef 300mm f2.8 mk II or a ef 500mm f4 mkIII shouts volumes too. I suspect that the RF 100-300 f2.8 and RF 200-500 f4 were on this map an long time ago and shaped the direction of big white lens developement.
While I agree that the 200-500mm f4 will probably be heavier and bulkier than the ef 500mm f4 II, it will be an exceptional optic. Canon do not drop the ball often and lenses like the EF 50mm f1.2 L are rare. I suspect the weight of the RF 100-300 F2.8 and 200-500 f4 will be addressed in about 5 years time with the mkII version
