This is very sad news. My condolences to the Koetsu family.It is with sadness when I heard that Fumihiko Sugano passed away last August 21. For us Koetsu lovers here, we would miss his legacy , and his great continuation of his father's endeavor. Treasure your Koetsus and take good care of them.
I hope that they have a succession plan in place. In Japan it would be traditional for the eldest son to take over almost without question, but I have not heard or read anything about this planning before.
It would be not optimal IMHO if Koetsu was sold to an outsider, I feel that similar to wines, it's not just the terrior that one seeks, but also the taste of the winemaker and other intangibles such as heritage/history.