Wow. Not for the casual shooter! I s'pose the audience for that will be the various agencies doing sports coverage, initially.
Got my eye on a 200~500mm AF Nikkor β±4 on E-Bay in need of repair. We'll see if my offer is accepted. If so, it'd be a "nice-to-have". But with what we have for prime, wide-angle and short to medium zoom glass now is certainly adequate for our use. Plenty of focal length overlap. The 80~400mm was bought on speculation at a good price compared to what it was when new, but somewhat wanting IMO where sharpness at full extension is concerned. Still playing with it, though.
Yesterday Mitsy had a delivery to make for a client of hers and stopped later at the "turtle pond" with her camera. She got a couple interesting shots of some birds and a dragonfly. The turtles were apparently still on spring break tho. Only one and high noon lighting was too contrasting for a good shot.