Nikon's 400mm 2.8 isn't "super light" at 3.8kg compared with Canon's RF400 f/2.8 at 2.9kg . The built in T.C is great thoughNikon has been pushing the RF sports lens theater with the introduction of the 120-300 F2.8 for indoor work, and the super light 400 2.8 with built in 1.4X. As an owner of the Canon 200-400, 600 F4, and the RF 100-500mm. I have found the new 100-500mm to be a terrific alternative to its much heavier cousins. I would not sell my 200-400 to get the proposed RF 200-500, but the 600 F4 would be out the door ASAP if a RF 400 2.8 with 1.4X became realty. FYI: I never carry the 200-400 & 600 to the same event. Which one I use totally depends on my access to the players (footballers, etc).