I wonder if they will develop a 400/5.6PF? That would seem to strike a good balance between reach and affordability for many amateurs, and give better quality than zooms or 300/4+TC which cover the same range. Nikon is rather lacking in 400mm primes apart from the 400/2.8.
A Nikon patent mentions 400/5.6, 500/5.6 and 600/5.6, all PF. But of course we cannot know which of them (or if all three) will be realized into products, apart from the 500mm which was announced to be in development.
Given that there is already a 300/4 PF, the annoucement of 500mm next makes sense since 1.67x is a reasonable ratio between consequtive focal lengths that you might carry at the same time. 1.33x is perhaps too dense a spacing between primes, in my opinion. I understand the cost argument but a new 400/5.6 would likely be priced quite high (2500-3000€?). This would make it a hard sell when compared with the Canon 400/5.6, which has been in the market for a very long time. 500/5.6 has some novelty which means the price is not dieectly compared with existing older products.
Which would I prefer? As a user of 300 PF I would like to add a 500/5.6. Of course, the cost is a big issue, and the lens needs to be high quality, reasonably fast and accurate focusing, and lightweight and compact. We know the length but it is interesting to see how the tripod collar is; is it built in and non-removeable, fully removeable or with removeable foot but not collar? How well does it handle vibrations? Etc. How much image quality is lost compared to the 500/4G and E VR and is there some area where the 500 PF is actually better? For example, LoCA could be very well corrected and it may be optimized for near distances and offer a high maximum magnification (for small subjects a fast maximum aperture may give too little depth of field, whereas for large or faraway subjects the f/4 aperture is beneficial and useful).
If it gives excellent close up capability with high level of optical correction, and yet give better results at longer distances than 200-500, and very good corner sharpness (I am thinking about architectural and landcape details not only moving subjects) then I think it will find its users. I don't care for TCs, and happy if lightweight long glass is made available so that I never have to use a TC.
If the image quality is not as good as the 300 PF then I will not be trying to stretch myself to be able to afford it, rather I will consider the second hand market for the 500/4 VR. I have tested it a bit (G version) and liked it a lot, but currently I have some back pain (having been foolish enough to lift something extremely heavy at work, now suffering the consequences) and so I have to consider the PF to be on the safe side for recovery.
