Agreed - definitely.
My hunch about the D850, is that it may well be the last of the top end advanced amateur F-mount DSLRs from Nikon and as such will be sought after by those with significant collections of F-mount lenses that want to use such lenses natively without adapters.
That's exactly why I have an 850. It has given me a reason to keep all my F lenses and not sell them. Also love how it sounds.
As for the 810, never liked the camera, didn't like the pictures - color, exposure, clarity of view, whatever. It's the only Nikon camera I have never really liked. Of course, maybe it was a lemon; or perhaps, user error.