Nikon patent application 20120182617 is for a 300mm f/4 with VR. The interesting part is that the overall length of the lens is relatively short ~ 190mm (around 7.5 in.) with back focus - so real length would be ~150 mm, much shorter than the existing 300/f4 (222.5mm/8.8 in):
In the patent calculations one of the surfaces is marked as "Diffraction surface" which is probably the reason for the compact lens size. I believe this is the first full lens patent with diffraction. See also Canon's explanation of the Diffractive Optical (DO) element.
Nikon also filed a patent in Japan for a 100-230mm f/4.7, 18-55mm f/3.5-5.6 and 18-200mm f/3.5-6.7 lenses: