We've been following this for a little while to let some meat stick on the skeletal rumors, and it's finally feeling substantial enough—though definitely still a rumor—to throw your way. It looks like Nikon's got a 41-megapixel medium format (MX) sensor up its sleeve, which is most likely for a digital rangefinder. Nikon itself teases something BIG for the Wedding & Portrait Photographer International convention in Feb. in the pages of Rangefinder magazine. Finally, Nikon Watch has a tip (albeit unsubstantiated) that the MX format sensor is 48x48mm and in fact 48MP, and will go inside of a digital rangefinder that's "not to [sic] dissimilar to the older film Mamiya 6 camera philosophy." There's more. Obviously, a new format means you'll need new glass. But, the tipster says that the rangefinder will be able to use DX and FX lenses with a mount adapter, giving you crop factor of 1.5 for the DX, 1 for the FX and 0.5 for MX lenses. When shooting with FX,you'll be able to rotate the sensor crop from landscape to portrait instead of having to turn the whole camera, and somehow you'll still get to shoot the full square resolution. And yes, this thing will have live view. Given Nikon's penchant to leak like the Titanic, we'll know more about this puppy soon, no doubt. [Nikon Rumors, Nikon Watch - Thanks Peter!]
I am highly skeptical this is going to be a rangefinder camera. Nikon has been out of the rangefinder business for quite a long time, and so having to bring itself back into this design loop would be very inefficient. Their real design expertise for quite some while has been in SLR development. As such, I would expect them t be far more likely to stick with this technological fork.
While they may be working on a medium format sensor (although the "proof" behind these rumors is still more than a bit sketchy), the basis for rumors that it will be for a rangefinder camera seems to be based largely off wishful thinking, wild-ass guesses ,and from the fact that there was an ad in Rangefinder magazine (which by the way, is NOT a magazine about rangefinder cameras, it is a general interest photography magazine for professional photographers, with a strong (but not exclusive) bent towards wedding and portrait photographers). Maybe I'm wrong here, but I just don't buy it!