Just to clarify - the new Nikon Pro lens on the way is 120-300 f2.8 (as per the press release). It seems to be the 'FL' replacement for the 300/f2.8 that never arrived. As such you could probably expect excellent IQ across the frame and range, and I think it's likely to be released alongside the new D6 flagship camera body.
Using a lens like this will give you a 180 - 450mm equivalent focal range on the crop body D500.
There's no free lunches though - if you are looking at fast aperture lenses to keep the ISO down then they will be heavier than their slower aperture equivalents.
I'd imagine you'd want as much light as possible and zoom capability for maximum flexibility.