RCS messaging has appeared in iOS18, and even though WWDC2024 is a great opportunity to detail its plans, so far there is no active RCS messaging in the IOS18developer beta that Apple plans, but some of the relevant code is hidden beneath the surface of the Messages app. It seems to be. 

In fact, one person who goes by the name Dhinak G on X claims to have been able to get that code to run — activating some RCS messaging features on the iPhone. This was obviously not intended to be used and was not a finished product, but the eye on how the RCS/iMessage system works

The features currently available include basic features such as delivery status, file sharing, and group chat. But a bunch of features are obviously not working right now, the most important of which is end-to-end encryption. That was one of the reasons Apple kept RCS for a long time.1

Other missing features do not include broken replies, reactions, or read receipts in group chat. Needless to say, there is definitely a reason why RCS is hidden in the iOS18developer beta, and this does not indicate how the final version of the feature will work. 

RCS messages are expected to appear in green bubbles, and according to Dhinak G, there is a toggle in the settings to turn RCS messages on and off. The message also appears to be green, not iMessage blue, which is what Apple has already confirmed.

Dhinak G also speculates that the system is running on Google's Jibe server.The Jibe server is the same RCS profile used by Google Messages and other RCS messaging services. In that case, you need to ensure interoperability between Google Messages and iMessage.  However, I'm not sure for sure until Apple activates RCS messaging in a future version of IOS18. Perhaps it will be available in beta initially, but for now we don't know anything about Apple's deployment plans. 

The fact that there appears to be a very rough version of RCS hidden in the iOS18 developer beta code confirms that Apple is working on it. But for now, we just need to be patient and wait to see what happens. In the meantime, check out all the new iMessage features included in Apple's iOS18 update.