I think the Df has had its day in the sun and to be honest I found the control layout kind of odd. I always thought it would have been nice if Nikon had put a control dial around the throat of the lens mount instead of that small thing on the upper front right of the camera, plus they got a bit carried away with dial locks.
For me I'd go D850 though I'm still waiting to see what Nikon does this year (pretty please, a D850 update with the D6 AF sensor and the Z7II imaging and PDAF sensor, and I wouldn't say no to simply plopping in the Z7II chipset while they're at it though I don't expect IBIS). I'd rather not start over again with mirrorless.
To interest me a new DF would want probably one of the Z-body imaging sensors and the EN-EL15 battery, and a cleaner overall design, looks and ergonomics wise a bit more F3HP or F4 base and a bit less "designed by committee". And of course the lens throat control dial for dealing with aperture control on those G and E products and exposure comp on everything else.
But while we're at it, have Nikon ever thought of trying to do a new film camera that supports the E lenses? Or is this film revival a temporary fad that's going to winnow down to a handful of medium format diehards?