With Canon and Sony coming in with ~6.3lb (2.8kg) lenses, it's kind of a joke having an 8.4lb (3.8kg) Nikon offering. it's a great lens, but 1kg is a lot of weight to save.
Any hope of relief soon?
The 500 f/5.6 PF is very light, but starting to get pretty slow for birds in flight or sunrise/sunset wildlife photography. A 500 f/4 (or 400 2.8 + 1.4tc) to f/5.6 is half the shutter speed.