The only reason I'd buy right now is if I was either a landscape photographer or someone who needs large prints, but doesn't want the bulk of a D850
That's exactly why I'm so excited. If you're wondering "who did Nikon make this for that doesn't already own lots of F-mount glass?"...it's me!
I love the size and handling of my m43 kit, but the dynamic range and resolution often leave me with a tinge of regret. I'll be unable to resist 8k displays in a few years, too. Between my distaste for tripods and moving leaves, pixel shift hasn't been a major plus for me.
I've been considering an a7r mk2/3 as a secondary, larger system, but I'm not really happy buying into the Sony camera line. Poor handling and no weather sealing mean a lot to me, and while those could be fixed in a new body, the cramped mount can't--I think the vignetting crosses from 'nuisance' to 'problem' on the 24-105/4, for example. So in the short term the bodies don't do quite what I want, and in the long term the mount doesn't do what I want.
Then, Nikon announced a system barely bigger than my EM-1mk2+12-40/2.8, with a glorious d850-like sensor, what appears to be good handling, weather sealing, and a futureproof mount. Of course the specialty lenses don't match what's available on m43, and the 75/1.8 may never be replaceable, but I could easily see this being the only camera I need in a few years. The 24-70/4 can probably do about 60% of what I need all by itself, and based on the edge-to-edge MTF performance I'm not sure I'll find a better lens for lightweight travel/nature/landscape in the next
decade.