Nikon announced the development of a 500mm f/5.6 PF lens. The lens will contain the same type of PF element used on the 300 f/4 PF and be relatively small in size and weight. Pricing and availability will be announced later this year.
This looks like a great new lens. The 300 f/4 PF is wonderful and delivered in a small, light form factor. This promises to be similar.
I'd expect this lens to be sharper than the 200-500 and near the performance of the 500 f/4. It will probably work pretty well with the 1.4 teleconverter with good light. And more importantly, it will be very easy to handhold or use with minimal support, good for birds in flight and similar action, and much better for travel. As a travel lens, for travel to Africa, South America, or similar exotic locations, the lower weight and compact size make this lens a great choice.
Pricing is pure speculation right now. The 300 f/4 PF sells for $1996 US. My guess is a price in the $3000 range would make it a top seller and it's possible they could sell it a little lower. It's probably worth considering even at $4000, but then you have to consider the alternatives like a used 500 f/4 VR or just stick with the 200-500 or 300mm f/4 PF.
It's interesting that nobody is selling a 500 f/5.6 lens right now. With better high ISO performance and better focus, it sounds like there is a good opportunity. The much lower price and smaller size make this lens very attractive. The 200-500 is excellent, but focus is not very fast and it's not prime lens quality.