The GSMA published a blog post to announce the new features coming to RCS. The iPhone is getting end-to-end encryption RCS messages via the Messaging Layer Security (MLS) protocol:

The new specifications will use RCS Universal Profile 3.0, a cross-platform encryption protocol that will make it easier for iPhones and Android devices to identify each other. The profile allows for richer deep linking,

In a new announcement, Apple said it will add support for encrypted RCS messages in future updates to iOS, iPadOS, MacOS, and WatchOS. This means that any rich text messages exchanged between Apple and Android users will automatically be secured through the latest industry standard.