Nikon is rumored to announce a new Nikkor AF-S 200-400mm f/4E ED VR lens towards the end of 2017. The lens will be equipped with a built-in 1.4x extender just like the latest Canon version. Optical quality is expected to be extremely high and so will be the price (the current models is priced at $6,996.95). The new lens will mainly be targeted at sports photographers. Shipping should start before the 2018 FIFA World Cup that will take place in Russia from June 14th to July 15th, 2018.
The 200-400mm has been on the list of lenses that will get updated with a fluorite element (FL). I will have more information on this in the coming months.
Two more Nikkor lenses are rumored to be announced this year (I expected 5 new lenses, 3 were already announced). One of them could be the Nikkor AF-P 70-300mm f/4.5-5.6 VR full frame lens and the second should be the Nikon AF-S Nikkor 200-400mm f/4E ED VR.