There have been no rumors about the 880 for over a year. I expect that the replacement for the d850 is the Z8. As much as some people love optical viewfinders, I don't think Nikon can support leading edge development on mirrorless and SLR at the same time. Current resources are going into computational AF, processors, improving EVF, and optics. While some of this is applicable to SLR cameras, advances in AF, processors and (some) optics are different for mirrorless. This means parallel efforts would be needed to keep pace on the SLR side, At some point it will not make sense try and keep up. I think that point has already passed. but surely there may be different opinions on when it will happen. I have no doubt that it WILL happen.