I don’t think that either Olympic or Coronet would have happened. Especially after Okinawa and Iwo Jima.
There would have been a naval blockade and continued conventional bombing. There would have been magnitudes more Japanese deaths from that than from the atomic attacks. And that’s not counting what the Sovs would have done to the Japanese army on the mainland.
Remember Tojo and company tried to kill the Emperor before he made his broadcast that convinced the Japanese to surrender. Had their plot succeeded, who knows what would have happened.