https://www.sonyalpharumors.com/last-minute-wild-camera-rumors-one-of-the-new-cameras-is-the-a7riv/This came a bit earlier than expected - the A7r3's less than two years old, and the A7s3 isn't even out yet. I guess that means Sony has come out with enough cumulative improvements to justify a new model.
Despite primarily shooting cityscapes, landscapes and other things not particularly taxing on the autofocus, I'm actually l more interested in the A9II than this. Pumping the resolution to 60-70MP will only eke out incremental gains - atmospheric effects and other non-sensor-related issues tend to kill resolution at this level, so there are few subjects which would benefit from this and can'tbe stitched (for even better results). Obviously, it's a different case if you're shooting studio portraits, advertising work or art reproduction, particularly if Sony's made their next generation of bodies more flash-friendly. It would take something else - an extra stop or two of DR, a global shutter, several stops of improved noise and DR at mid-ISOs (1600-6400), for instance - to make it particularly compelling.
If the A9II manages 36-45MP while retaining top-tier AF, and particularly if it has a global shutter (although I doubt that's ready for the coming generation of cameras) it would be much more interesting than an A7r4 which is just an A7r3 with 20-30 extra megapixels. It would allow the same camera to function as both a primary landscape camera and top-tier wildlife/action camera, simplifying the logistics of mixed-shooting trips. Of course, that depends what else the A7r4 brings other than increased resolution, and how many of these features are unlikely to also show up in the A9Ii. At the moment, the A7r3 and A9 make a great combination. The next generation could well consolidate both roles into one body - whether it's the A9II or A7r4 which fulfils this role better remains to be seen.
That said, I'm very interested in what they've come up with in terms of new technology. The 42MP sensor is getting on 4 years old now, so the new camera will, presumably, use a new sensor based on updated technology. Anything that shows up here has a good chance of also showing up in other new models.