New Nikon Z9 flagship?

I agree. The 400 f/2.8 is certainly a staple for sports photographers. If you are going to embrace the Z9 as described, that lens is required.

Sony has the Getty contract for this rotation. They have to deliver the 400 f/2.8 to fulfill that contract. The sad thing is those contracts don't make any money for the manufacturer. There is a lot of pressure on that gear being better than gear from Nikon and Canon - otherwise why change. And Canon is rumored to have a full suite of long lenses around the same time.