A 2.0/200PF could be something that would interest me though.
According to Nikon, the weight savings from PF in the fast teles (as well as zooms) would be lower (than in a 300/4) and the users of the fast teles tend to be finicky about bokeh. Nikon say they can make these lenses better using other methods. Likely this means FL and now also SR. Also, they say the PF lenses are not quite as rugged. I'd be happy if they make an FL 200/2, but then again I'm happy with the current version as well. ;-) I would like a more modern focus motor in the lens, though.
Nikon could make an FL 200/2 but who knows, it is a lens with a rather small market. On the other hand, Nikon now have a rather small market as a whole, so maybe it would be a good fit. ;-)
It seems the race is up for the maddest collection of wide-aperture lenses, with Canon being very active. They seem to have patents for 18/1.0, 135/1.4, etc. A 135/1.4 might actually be an easier-to-handle way to get 200/2 -like results.
Apart from birds (where 500mm might be seen as a little short sometimes), I've found the 500 PF to be great for mammals. Mammals tend to be spooked if I set up a tripod so this lens permits freehand shooting from car easily, and also on foot. I can walk in the forest and sometimes get a shot that way as well. With birds I actually prefer to use a tripod (also with this lens) and wait for them to come to a suitable spot. But maybe I'm the only photographer who mounts this lens on a tripod. :-D