Not sure how reliable this info is. But a source at Xitek claimed this:
“Just spoken to a franchise director at LCE, apparently Thursday will be a very exciting day indeed.
The adapter for the new mirrorless camera will pretty much be free when bought with either model, and the adaptor will make upto 400 lenses compatible so that’ll make all lenses with either electronic or mechanical apertures compatible.
The sensor will be better than the D850 owing to how they’ve constructed the diodes and the way it’s capturing more light, and the new range of lenses will have fresnel elements to give an ‘effective’ larger aperture (so I was told a 1.8 Will be marketed as 1.8 but behaves like a 1.4, and be tiny) much like their new 300mm that shrunk.
Pre orders coming Thursday to ship mid November”
Just chatting with the LCE branch manager, he said that obviously Thursday will be a very exciting day.