As Babelismoj says, you can now set your games to private, both at the time of purchase as well as once they're in your library :)
But also, "demos" will continue to be posted on Itch even if the Steam move happens, so you'll still be able to play the public version here as normal!
And if enough people shift over to SubscribeStar then I won't have to move to Steam at all, and I can finish CK just as I started it!