Nikon will allegedly announce two new Z-mount lenses along with the Nikon Z9 flagship full frame mirrorless camera. Official announcement will probably happen in November/December 2021:

The Nikon NIKKOR Z 400mm f/2.8 S Lens is expected to have a built-in 1.4x converter just like the AF-S NIKKOR 180-400mm f/4E TC1.4 FL ED VR lens (with the TC the focal length will be 560mm).

Nikon is fully committed to the future of the z system with a total of 27 amazing lenses and 2 teleconverters that will be available by the end of 2022.
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