Sony is expected to announce a new high-end full frame E-mount mirrorless camera soon, probably ahead of IBC 2019 this month to early next month. Sony currently has one new camera code “WW942051” registered, this camera code has same 5.8GHz Wi-Fi as Sony a7R IV, so this camera could be Sony a7S III or a9 II.
Recently, Panasonic has just announced the S1H cinema full frame mirrorless camera, and also Nikon will soon announce the D6 flagship DSLR camera. So both a7S III and a9 II should coming soon. Stay tuned.