The industry at large and Apple in particular is coming at them from the other direction preferring premium, furthering ad blockers and offering better privacy defaults (iOS 11). Elon Musk has gone so far as to allude that Google is the only AI company that worries him[1].
And so it goes. Coupled with AI and the amount of data they are able to feed into the AI engines, I am guessing this won't regress their ad targeting.
They have also managed to supplant it with other avenues. Google Travel, Google Calendar and other apps have explicit permission to read your email, Google serves email images off their own servers which gives them a tracking beacon and behavioural data across cohorts. All this adds a level of indirection but still gives them access to behavioural data and user intent.