Right. So Nikon will release an A7-like camera, with higher resolution than the A7r3, with better AF than the D5. And pigs might fly.
Re: AF performance. A7III tracks over a wider area of the sensor. A7R3 has better eye AF (works at a greater distance). Both seem just as fast tracking something within the area of their respective PDAF zones.
I don’t think this scenario is likely at all. We’re all guessing here, of course, so here’s mine...
I think, based on the Nikonrumor site’s releases, that there will be two cameras in quick succession, if not at the same time. One will be a high-res tour-de-force camera in the D850 class that competes with the A7R3 in features and bests it in resolution and ergonomics (for many people). I think it’s autofocus will be very good, but not D5 good, and I expect it will have all of the technology tricks of the D850 like automated focus stacking and time lapse. And I expect (maybe the right word is hope) that it will have the best, highest-scan-rate, highest-DR viewfinder on the market.
I expect the other camera to be a 24Mpix, A73 class camera—a camera with a lower price for a larger market, with very good low light performance and autofocus, but not D5/A9 class autofocus. To do that would make it cost too much for this target market.
Next year, I expect at least two more. One will be an A9 class mirrorless with top-shelf autofocus and frame rates and a price to match. This one will be in the 24Mpix range, because all of the class-leading autofocus cameras are in that range: D5, A9, 1D, & SL all twenty-something megapixels, and I think that’s not just coincidence, I think physics are at play there.
The fourth camera, I have no idea. If Nikon really wanted to make a splash in the video world, they’d release a low-light monster that records 10-bit, high-bitrate video, and outputs 10-bit uncompressed to its HDMI port. If it can autofocus video well, that camera would turn a lot of heads.
Or they could go the APS-C route with the fourth one, though that requires another set of lenses.
That’s my prediction, with the benefit of no actual insight or inside info at all. Anybody setting up a pool?