Hi Bruce
I'm also similar to EricB. The 70-200 f2.8E FL continues to serve up keepers, and often with a TC14 III.And its 70mm end is often most useful. I'm also very very fortunate to have a Used 180-400 f4E TC14 (for a decent price). The 800 PF is my 3rd key lens for
African wildlife (in savanna habitats).
I use both these zooms across both the Z9, D5 and D850, although the 180-400 tends to glued to the D5. I've held back from the excellent 100-400 S waiting to see how this smaller 400 prime turns out. Perhaps I'm biased because my first telephoto was a 400 f5.6AI on the FM2 or F3 and ideal for hiking etc at 1.2kg (72mm filters).
However this heavy zoom is slower for snap shooting, and hiking. Here I anticipate this 400 PF will be ideal, and also pair well with the ZTC14. Quite a few 300 PF owners often use this dinky prime as a 420 f5.6 (and it also works surprisingly well with TC17).
So a 400 f4.5 / 560 f6.3 is going to be versatile in key respects for many wildlife subjects.
You are fortunate to have so many options.
I have sold much of my redundant gear and am now working with a much smaller kit. This decision is both by design and dictated by economics. Due to her health, my wife is not shooting any longer. Our last photo trip was in March to photograph birds of Texas. At that time, we had a pair of Z6ii's, Z7ii, Z7, D500, 500PF, 200-400 f4, 100-400S, 24-200 Z, and 24-70S. The Z9 was not affordable, and I used the D500 for taxing AF tasks. Three months later, I sold half of my gear, banked some cash, and purchased a Z9.
During the "fire sale," I had to make a choice... build a kit around the 200-400, or build a kit around the 100-400. Because I chose to put $5500 into a camera, I decided to design my kit around a Z-optic... the 100-400mm lens. While there are many days in which I wonder if I'd been better off going with the 24-200, 200-400VR, 500PF, there are as many times that I've benefited from the tripod-free shooting that is possible with the 100-400.
Unlike many photographers, I find most of Nikon's glass to be good enough. I'm not necessarily impressed by the sharpest or fastest lens... I am actually more impressed by composition / processing decisions, and will ignore minor optical imperfections. As such, most modern lenses are good enough for me.
So, in keeping with the actual theme of the thread... It is great news that Nikon has pushed out a Z-mount telephoto prime that is less than $4000 (at least I hope it's less than $4000
), I just don't know if it is a replacement for a modern and high quality 500mm PF lens when you need to shoot at 500mm.
When I look at my work throughout the past two years, about 60% (20000 +) images are with the 500PF. This suggests that 500mm is the minimum focal length I need, as most of these pictures were taken with the D500. It is for this reason that I am looking for a way to pair my 100-400 with the 800PF. If Nikon does not introduce a high-end DX body, I think that I will be looking to build a kit that consists of 24-120. 100-400, and 800PF. However, to be clear, the 200-600 is the wildcard. It this lens has an internal zoom and maintains an f/6.3 aperture at the long end, it might be a better option for me... I could envision a 24-70, 70-200, 200-600 kit.... so many options. But, until Nikon actually releases this lens, is continues to be a unicorn to me.
bruce