I agree- but dont like the forced choice either - Nikon has promised to further support SLR line - what we have seen is only discontinuation and the 120-300 mm lens as latest new product? (I know about the forces market development)
For some time there will be enough copies available for backup purposes.
I would assume that a D850 replacement is in the works, but obviously things can be changing quickly and the ongoing pandemic is affecting both customer motivation to purchase new gear as well as production. On top of the pandemic is the so-called mirrorless transition.
Personally I am one of those who prefer OVFs and have taken measures so that I can continue to use them. I will use the new tech when it is needed (when a DSLR would be too loud, mainly) but I'm not entirely keen on it, and the D850 continues to be the camera I pick most frequently.
I would prefer continued availability of DSLR gear but of course I understand that manufacturers are subject to market forces.
I suspect the D500 would be on its way out even without the mirrorless transition as the manufacturers prefer to charge 6k€-8k€ for high performance instead of <2k€. Of course, users may have the opposite wish. Component availability problems arising partly due to the shifts in spending but also due to production disruptions affect lower-priced products more than high-priced ones as the component manufacturers are keen to prioritise deals where they get paid more money per part, and this is why manufacturers are putting orders on hold for being some of the lower-priced cameras as a deal may not be possible to strike with a sufficiently low price and high volume.
If Fujifilm can put out a stacked DX BSI sensor in a high-performance mirrorless camera and if it turns out competitive with the big three then this might add some pressure on Nikon, Sony and Canon to produce a competing offering. Olympus also have the 150-400/4.5 TC but to my knowledge they don't yet use a stacked sensor in their camera line.