Another endorsement here for mirrorless.
I'm a long-time Nikon user (since 1991); last did a major overhaul of my system in 2012-13 with the D800 and some appropriate lenses, and had been waiting for a meaningful upgrade to that. The D850 would have been it but no PDAF on the sensor was a dealbreaker as I'd always maintained that to get me to shift would require a proper hybrid camera. Nikon were reported to be field testing a D850 replacement (D880?) in 2020 which would have been a counterpart to the D780, their 24MP hybrid DSLR with full PDAF on-sensor for video, but then covid hit and then their leading component supplier factory in Japan burned down, and they were left unable to support both DSLR and mirrorless at the same time. When they came out with the Z8, that was effectively in mirrorless what a D880 would have been in DSLR. And I think it's a great camera.
Now even the D6 and D850 are being discontinued.
I'd strongly recommend any of the Expeed 7-based mirrorless cameras in Nikon's lineup; overall their performance is a big improvement over DSLR, video is better in every respect, autofocus improves in many more ways than it regresses (though the problems mirrorless cameras inherently have with level horizontals remain, only the Canon R1 has come close to addressing that one that I know of), and now that the viewfinders on the latest models refresh at 120Hz instead of 60 it feels much more immediate to use them, no longer like you're watching a broadcast rather than the real thing. The Expeed 6-based Nikon mirrorless all only have 60Hz finders and can't always keep up on autofocus with moving subjects, though they're fine for portrait and landscape; Expeed 6 is more than enough for the very best of traditional DSLR autofocusing for photos, but for the video-supporting phase-detect autofocus on the sensor that mirrorless cameras depend on for both stills and video, it's not enough power to do the blend of PDAF and contrast detection that really good mirrorless AF requires. Hence Expeed 7 in Nikon, DIGIC X in Canon and so on.
I still don't think any mirrorless or any other DSLR equals a Nikon D6 for autofocus for sports & action photos (as opposed to video AF where the D6 is poor), but the latest mirrorless bodies are getting close.
