[JJ_SO]

First, "in the work" is something else than "you can order it right now" - the 500 PF E is a very good example that demand exceeds supply (1000 copies/month...).
Second, no one knows how good it will be, how much it will cost and how much lighter than Sigma's 3.4 kg cylinder. (that was already third and fourth).

I think, Nikon wants to win over the sports photographers who are hesitating because the internet knows how ohhh so bad Sigmas focusing. The 58/0.95 was also announced to be in the making, as well as the Z-line's battery grip. Nikon starts with vaporware, no?

It was just my answer to what SR might mean :-P

Well, you need to hammer the S and R a bit less humble... like SR which also could mean Sony Rival