Photo by Lilly Rum Nikon Rumors has gotten wind of a very interesting bit of plausible speculation—at this point, we're not comfortable calling it any more than that. According to the rumor site, the Nikon full-frame mirrorless people are hoping and praying for will sport an all-new so-called "Z-Mount".
The name is probably still not final at this stage, but NR is reporting with some confidence that the Z-Mount will have an external diameter of 49mm and a flange focal distance of 16mm.
We obviously can't know if these numbers represent a real mount in the works at Nikon, but we can confirm that the numbers add up. While 16mm is very short, if you have a camera with a wide enough diameter it kind of doesn't matter. The back of the lens could be further forward than 16mm, so long as the mount doesn't intrude.
For comparison's sake, Sony's E-Mount (the shortest to be used with a full frame sensor) sports an external diameter of 46. 1mm and a flange distance of 18mm.
As always, we have contacted a Nikon representative for comment, and will update this post if and when we hear anything official from Nikon USA.. dpreview.com