Nikon has released the AF-S NIKKOR 500mm f/5.6E PF ED VR lens last year, and currently is still out of stock everywhere, you can pre-order at Amazon, B&H Photo Video, Adorama, Focus Camera. According to a user on dpreview forum, Nikon is rumored to announce a new AF-S NIKKOR 600mm f/5.6E PF ED VR lens this summer.
In the next several months of 2018, Nikon is expected to announced around three new cameras and 2 new lenses. At least one of these cameras will be Nikon full frame mirrorless cameras. Below are a list of rumored Nikon cameras and lenses to be announced in 2018.
According to trusted source from NR, Nikon is planning to announce a new AF-S NIKKOR 600mm f/5.6 PF lens in next several months, the announcement time is likely in this Summer, June to August timeframe.