Imaging-Resource has posted first high ISO images of new announced Sony Alpha a7R III (Amazon/B&H Photo/Adorama/Focus Camera). And here are first comparison images of Sony a7R III with Nikon D850 and a7R II.
From the comparison, we can clear see that Sony a7R III has better image quality than a7R II, and compared to Nikon D850, it seems that a7R III is also a little better. You can see more detail at Imaging-Resource.