But Google really has no choice here due to aggressive campaign by Mozilla, Apple and Microsoft who boast with their Intelligent Tracking Prevention ( https://webkit.org/blog/8828/intelligent-tracking-prevention... ) implementation blaming Google as a company which does not value users privacy. Google would lose privacy-conscious users otherwise.
But it is clear for me how all this anti-thirdparty cookies situation will go further: server side third party ad trackers -- this will bypass Same Origin Policy and will pose a privacy and security threat for users and websites even more than todays third party frontend ad trackers.