I'm pretty sure people will hold on to their D850 for a long time
The first set of lenses will most like be fixed focal length f/1.4 I agree with NikonRumors on that
Noct if ever,,, much later,,, true the Z-mount is capable of fast lenses but i'm pretty sure high ISO capability is 'ruining' more or less the need for a Noct as the first lens,,,