It has already disabled the ability of 3rd party apps to perform tracking locally while preserving privacy by "disabling the ability of apps to share data locally within a device". If you click an Amazon ad on Facebook and open the Amazon app, Apple will not allow Amazon to report a successful conversion locally (thus preserving privacy) to the Facebook app.
However the same restriction won't apply to Apple as they are the operating system.
Note that Apple is always complaining about "privacy", not Ads. They are going to go all in on Ads.
[1] I suspect law enforcement will still be able to access the local data from the phone, so the privacy preserving tracking might not work when you need it the most.