Tony Northrup posted the first comparison between the Sony a7R III vs a7R IV JPG images. The difference is bigger than I had expected:
Sony A7rIV and new accessories:
Sony A7rIV in USA/CA at BHphoto, Adorama, FocusCamera, Amazon, Henrys.
Sony A7rIV in EU at Calumet DE, ParkUK, WexUK, Calumet NL.
Sony A7rIV in Asia at Sony Japan. Sony Australia.
Sony VG-C4EM grip in USA at BHphoto, Adorama, Amazon, FocusCamera, ParkUK, WexUK.
ECM-B1M Digital Audio Shotgun Microphone at BHphoto, Park UK.
XLR-K3M Mic at BHphoto, Park UK.