Only Nikon knows what their extensive market research says and what their long term strategy is.
1. This is the one factor we can have confidence in. We can also have some confidence in the clear intentions stated in their April 2022 Investor Report
I have enough camera bodies.
I don’t need 60 mp , some people probably do, others think it needs to match what Sony or Canon have done.
2.Nikon will have had to initiate development / fine-tuning of such a sensor approx 2-3 years previously to release of such a camera. It's more likely Nikon will build such a camera on the existing 45mp Z9 stacked sensor. This will sell more of the latter and the tech entailed in the Z9 autofocus, data-processing etc
Nikon needs a D500 replacement DX semi-pro 12 Fps, deep buffer, good autofocus, 3d tracking, good 4K video. Good entry price and battery grip availability.
3. Such a camera should sell even more telephotos. However, the previous discussions of this Z90 invoke at least 2 factors: 1. the 200-600 replacing the 200-500 f5.6E, and 2. A DX stacked sensor will be a prerequisite to support the advanced features in the Z9 AF. A DX "Z90" should easily manage 20fps RAW, if not 30 fps, and use the Z9 dual data-path processing system, Z9 EVF: enabled with EXPEED7.
Nikon also needs a highly competitive mid range set of cameras to do what the D850 did for DSLRS in mirrorless.
4. see 2. above. Harder to justify more than 1 mid range MILC in the current market unless they have the additional stacked sensor. The Z9 AF has set a high bar, which a BSI Z6 or Z7 type sensor will struggle to support, even with EXPEED7.
5. Another important factor is the Z9 also kicked off what appears to be a fundamental change Nikon's in camera design - to part ways with the mechanical shutter. Will this become a trend as Nikon deploys Z9 level features "
across the lineup of its Pro/Hobbysists" MILCs?
6. Nikon has a history of springing surprises.
The Z9Sis at least 3 years away.
7. Based on previous cameras, Nikon could release a Z9s next year, if they keep the same sensor + EXPEED7. Change layout of a couple of buttons perhaps [card cover ?

]? However, it's hard to suggest what significant updates are possible without changes to the sensor and dual data-path processing system... e.g. if they to increase RAW frame rates, for example.
The Buffer is probably the most logical and feasible feature to upgrade.
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