I live in Sri Lanka where they’ve already done this. I guess we’re guinea pigs. The feed here is only friends and family. It’s murdered a few publishers, but most brands were paying anyways and they continue to pay for distribution.
This may actually make Facebook more money as non humans (brands, publishers) are forced to pay to play.
What this can’t overcome, however, is if your friends and families are toxic. Or, I suppose, you.