The problem with the transformation from Adam to He-Man is too much like when Billy Batson turns into Captain Marvel. It is standard 70s/80s super-hero cliche that happened often. Yes, it's what a lot of people remember from the cheesey Filmation show, but that does not mean it has to be used.
BUT, it seems that John Cho is a Filmation fan. So I think you Adam fans can rejoice that you will probably see a live-action adaptation of the Filmation show. The designs will be updated and cool, I'm sure, but there will be Prince Adam, Eternos palace, Captain Teela of the guard, bumbling ineffective henchmen, etc. that was the hallmark of that series. And to me that sucks.