The A7III kit is in Stock at BuyDig (Click here).
Alan Dyer (article here) shared a good news. He tested the new A7III for Astrophotography and the conclusion is:
“The Star Eater is gone. Stars are not smoothed out in long exposures.”
UPDATE: Jim Kasson has just started testing the A7III spatial filtering. And while there is no final conclusion yet it looks like the A7III may has not fixed this issue once and for all:
There was a recent posting to the effect that the spatial filtering (aka “Star Eater”) present in many a7x cameras and firmware releases at shutter speeds of longer than 3.2 seconds has been “fixed” in the a7III. The spatial filtering is different, but it has not disappeared.
This means we have to hold off and wait until Jim has made the complete testing.