With pretty much all mainstream mail apps using web views rather than the device browsers for links, they will close the redirect loophole. That will be low-hanging fruit. Third-party marketing platforms will have some tricks, but the privacy police will play whack-a-mole as they have been doing for years, already destroying attribution on iOS. Next year will be fun when Chrome finally follows through on third-party cookie depreciation too.Yeah, it will be interesting to see how Apple implements this.
It's very possible they will detect the 301 redirect of the shortened URL and auto-update the destination URL to have the tracking parameters stripped. I doubt they will leave such an obvious and easy loophole open.
Also, I've noted an uptick in traffic from "iCloud Private Relay" networks, which will make it harder to fingerprint devices.
About iCloud Private Relay - Apple Support
iCloud Private Relay — part of an iCloud+ subscription — helps protect your privacy when you browse the web in Safari.