If anyone in my circle of family, friends, and social network asks my advice, the formerly easy answer "Get a Mac, get an iPhone; you won't regret it!" is probably going to be replaced with something more nuanced ("Buy Apple, but know what you're getting into; here's a few articles on privacy....").
If it does come to macOS it will be part of Photos.app, as that's the only way to interact with iCloud Photos. I would recommend you to avoid that app and cloud in general if you care about privacy.
[1] https://www.apple.com/child-safety/pdf/CSAM_Detection_Techni...
- Communication safety in Messages
[…] This feature is coming in an update later this year to accounts set up as families in iCloud for iOS 15, iPadOS 15, and macOS Monterey.*
- CSAM detection
[…] To help address this, new technology in iOS and iPadOS will allow Apple to detect known CSAM images stored in iCloud Photos.
- Expanding guidance in Siri and Search
[…] These updates to Siri and Search are coming later this year in an update to iOS 15, iPadOS 15, watchOS 8, and macOS Monterey.