Nikon filed new lens patents for super telephoto prime lenses. These are 800mm f/5.6 (Already released), 600mm f/4 II and 400mm f/2.8 II.
The current AF-S Nikkor 600mm f/4G and 400mm f/2.8G was announced in 2007. Nikon may refresh these super telephoto lenses in the coming Winnter/Summer Olympics.
via: egaim