You can now see the full A7rIV versus A7rIII specs comparison table on this special BHphoto page. Something unexpected can be noticed: The new A7rIV has a slightly smaller sensor!
Sony A7rIV and new accessories:
Sony A7rIV in USA/CA at BHphoto, Adorama, FocusCamera, Amazon, BuyDig, 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, BuyDig, ParkUK, WexUK.
ECM-B1M Digital Audio Shotgun Microphone at BHphoto, Adorama, BuyDig, Park UK.
XLR-K3M Mic at BHphoto, Adorama, BuyDig, Park UK.