A source (Thanks!) sent me this:

Sony Semicron is considering mass producing a full frame sized 4K SPAD sensor with a global shutter in combination with their newest 2 layer transistor pixel tech. I don’t think this will be used in mirrorless cameras as the powerdraw is too high. Probably machine vision or very maybe cine cameras.

SPAD sensors use lidar technology for precise focussing. And if Sony develops a full-frame global shutter sensor, this would be an extremely interesting technology, especially for professional video applications. But as the source said, I don’t think this will be used in an Alpha camera anytime soon. I hope that the future Sony FX3II will use the same or an improved global shutter sensor as the Sony A9III .