A wide angle prime appears to be leaking variously to Sony and Nikon rumor sites, badged with the NiSi name, a respected third party filter and cine lens maker from China. Details were thin, but SonyAlphaRumors found the brochure for the lens to be released on Friday the 8th.
The lens appears from the outside to be a retrofocus design with a relatively small front objective lens [Update: confirmed by brochure].
Reflections visible from the front show it has 10 shutter blades. It is not designed to be a bokeh monster, but is likely quite good at sunstars.
NiSi’s filter system isn’t the most expensive out there, but it isn’t cheap either. A holding bracket with three neutral density 100mm square blanks costs about $400. A decent f/4 prime lens with autofocus could be expected to be priced at more than $500, and one without autofocus perhaps a bit less. Neither the Sony version nor the Nikon version pictured on the rumor sites appears to have an autofocus switch.
The firm’s cine lenses tend to go for about $1,250 around those focal lengths, but they’re typically more than a stop wider in aperture and, well, photographers are more skint than cine users. A launch video can be found here.