https://www.cnet.com/news/nikon-has-a-significantly-smaller-and-lighter-500mm-lens-in-the-works/

Nikon announced today that its developing a super-telephoto 500mm f5.6 lens with image stabilization that's small and light enough to be used handheld. 

Super-telephoto lenses are a prized possession for sports and wildlife photographers, but they are large and back-breaking to haul around. The upcoming AF-S Nikkor 500mm f5.6E PF ED VR, designed for the Nikon's full-frame FX-format cameras, uses phase fresnel (PF) lens elements that makes it possible to reduce the overall size and weight of the lens.