Well actually I think it's going to be different.
SMBs will only leverage Google, Facebook and other big platforms because I believe they'll have the ability to keep being relevant given their "walled-garden" model despite GDPR-like legal framework.
Every small publisher, aka 99% of them will likely collapse one way or another.
As counter intuitive as it might seem, while this would hurt their bottom line, Google and FB would benefit the most from this.
I'd rather see indie ad-networks with an emphasis on anonymity -no PII / control -delete profiles who works with publishers in a fair trade like model. But I'm not naive :(