While I personaly dont work on a Sideline in a stadium with Ethernet connected, I can certainly see that a higher resolution can be very beneficial for sports-photogaphers. It allows for much tighter crops, giving the editor quite some advantage. And Ethernet CAT7 is certainly fast enough to handle a bit higher data rates. 30mpixel instead of 22 shouldnt be that much of a problem, even at gettys editing/publishing speed, where an image is transferred, picked, croped, edited, tagged and published in less than 90 seconds. I think better crop options are great for sports.
Also: if they just include a "smaller jpg" option, for the people with incredible need for speed and high amount of pictures, than this topic would be solved
It also makes the camera way more versatile. Basicaly I could replace my 5D IV with it, if the 1DX III offers 30mpixel (or my Sony a7r IV which I just ordered). But for studio work, portraits, landscape and product shots, 22mpixel are not thaaat awesome. The higher resolution makes big prints, recomposed wedding photos and way better product shots possible (better retouch, cleaner cutout path).
Time will tell. As I use the current 1DX II for video projects, I am very exited for the Mark III, since its video options apears to be way advanced. Especially the unhandy codec and the missing hdmi 4k out on the Mark II are quite cumbersome. In Camera Canon RAW video is quite some heavy and welcomed upgrade in my opinion =) this alone may justify the upgrade for me =)