The extinction of the mirror is long, long over due. Kayaker and me where shooting at the Merritt Island Refuge, I had rented a sony a6500 (yes I know it is APC).
My 1dx at 12 vs. the sony at 11 fps. Everyone within 50 yards knew when the 1dx went off.... no one more than a couple of feet knew when the sony went off.
I would think effectively silent, no viewfinder blackout would be a "mission critical" aspect of a pro body. Same thing with sports - sure there might be a stutter but it is sooo much better than the mirror slapping up and down.