I heard this somewhat unusual rumor from a new source. So it should be taken with a grain of salt. But I wanted to ask if you would be happy if it turned out to be true:

I just returned from a West famous national park where I ran into a Sony professional photographer that is also a field tester of Sony gear. He mentioned that Sony is currently field testing  400 and 600 mm lenses that are 3/4 of the length of the current ones. Sony provides him photographic gear as a loaner when not assigned to a specific task. He photograph events such as football and other athletic events. I asked if he had to carry the Sony gear to the events and responded no; he just goes to the Sony Station at the location and his provided with whatever gear he needs to shoot the events.

He has no knowledge as to when these lenses will be released. I assume that to shorten the length of the lenses Sony may be using fresnel components. He was very reserved and had a Sony camera with no markings.

Sony currently doesn’t make lenses with Fresnel elements while Nikon offers this 500mm f/5.6E PF ED VR Lens .

In general, Fresnel lenses are lighter and shorter, but they have problems with stray light and a more nervous bokeh. These Fresnel lenses would be cheaper than classic lenses. As a Sony photographer, I wonder if you feel the need to buy such lenses for the E-mount system. I actually think it would be good if you at least had the option of buying compact and not insanely expensive telephoto prime lenses!