Nikon Rumors expects Nikon’s new Nikkor AF-S 200-400mm f/4E ED VR to be announced toward the end of this year (2017).
This new lens will have a built in 1.4 teleconverter taking it to a 280-560mm f5.6. This lens will be geared for the nature and wildlife photographer. Pair it with a D5 and/or D500 and you are looking at one whale of a combination. The current version retails for $6,996.95 so expect the new one to be well North of the current model. However, it may drop the price of the existing lens so the future will be full of options if you are willing to shoot with an older version of course.
You can read more about this over at the Nikon Rumors site: https://nikonrumors.com/2017/06/27/new-nikon-af-s-nikkor-200-400mm-f4e-ed-vr-lens-rumored-to-be-announced-at-the-of-2017.aspx/#more-113236