Let's not forget Nikon's mirrorless bodies and the Z-mount lenses. None of those, including the 24-70 f/2.8 S is natively compatible with F-mount cameras. Eventually - years from now, to be sure - Nikon may cease all new production of professional F-mount cameras and lenses. If that happens, it would most likely only be after a full range of high end Z-mount glass is available...everything from very fast primes to fast, long telephotos.
So, while it's quite reasonable to assume Nikon will continue to develop and release new F-mount glass - including high end professional lenses - for years to come, it wouldn't surprise me if 5-years from now, Nikon quietly makes the decision to focus 100% on Z-mount.
It is easier to get a photo of a bird in flight with the 300mm f/4 then the 500mm f/5.6 because of its wider field of view. Also a 300mm is smaller and easier to maneuver. So like most things, it depends on many things: how big the bird is, how fast it is going, how predictable a path it follow, how experienced you are, etc. So I would NOT say there are "focusing issues with BIF with this lens" but remember, a 500mm f/5.6 on a D500 is a field of view of 750mm for a 35mm equivalent. Putting the focus point exactly right on an erratically, fast moving bird will take some practice. And it is much easier in my opinion to photograph a BIF with the 500mm f/5.6 than with a 500mm f/4 or the 200-500mm f/5.6.
Photographing a RSH in flight with the 500mm f/5.6 lens on a D500.
Thanks for the feedback. I currently shoot with the D500 and a Tamron 150-600 G2 and it is usually without a tripod for BIF. I was just wondering how it was with the Phase Detection focusing system.