Recently, there are more and more rumors about the long awaited Sony a7S III. Based on rumors, we expected that Sony a7S III will be officially announced in the first half of 2020, around NAB Show in April.
Several months ago, a datasheet of Sony IMX521CQR image sensor leaked online: 15MP, Quad Bayer, 4K video at 60p, and 61MP mode. This sensor is likely to be used on upcoming Sony a7S III, you can take a look at full specs sheet below: