Sony's 70-200 2.8 OSS II undercuts the Nikon one in weight by 320 grams, and gets the lens element count down from 21 elements in 18 groups to 17 elements in 14 groups with an all-new design, though it's about the same size and like the Nikkor it zooms internally. I don't think it's really possible to improve the near-infinity performance of the lens, though closer up there are some possibilities for improvement mostly toward the 200mm end where corners see less resolution and stranger bokeh as you come within 15 feet or so and increasingly as you approach minimum focus distance. So I suspect this is the sort of thing we'll see from Nikon; a slightly simpler design with some fancy lens elements to get there, slightly better microcontrast, slightly better performance at near distances at the 200mm end, slightly faster autofocus, obviously less weight, and a clicky aperture ring. It's what Nikon more or less did with the 24-70/2.8 after all and it's what Sony has done with their 70-200.
Oh, and a bunch more money.
What might get me interested? If they find a way of really knocking it out of the park on close focus in a way that would allow me to skip a separate macro lens, especially if it can pull off something impressive at 200mm. Let's say the 50cm minimum focus distance of the existing 70-200 at the 70mm were to be carried all the way to 200 in the new lens without any blowback on optical quality -- that would more or less obsolete existing 200mm macro lenses.