We on the W3CTAG have been thinking about the web without 3rd-party cookies. And how to get there.
Our finding: https://w3.org/2001/tag/doc/web-without-3p-cookies/
"We consider privacy a core design principle and differentiator for the web platform…"
Improving the web without third-party cookies
This finding discusses the deprecation of third-party (AKA cross-site) cookies, the reasons for restricting them, and the challenges in removing them from the web platform.w3.org