I was really sure this was an early April Fool’s joke, but it appears to be genuine…
Apple will keep its iMessage protocol as-is, so that won’t affect its security, and they don’t want to bring iMessage either to Android (as that would lose them customers).
Right now, though, the Messages app on iOS is handling SMS messages, so they will add RCS to work alongside of iMessage inside the Messages app, just like SMS has been working. It will still show a green bubble in chats.
I suppose this move by Apple makes the most sense for them actually by keeping iMessage unaffected. Thing is though that RCS will then of course be a truly universal chat app that could also replace SMS finally. So many organisations are still geared around bulk SMS services, so it may be time for those services to start thinking about transitioning to RCS, which will probably save them a lot of money.
NOTE: Post was revised on 2023-11-17 to reflect RCS appearing inside the Messages app alongside SMS and iMessage protocols. The original post incorrectly stated RCS would appear in its own separate app.
See https://techcrunch.com/2023/11/16/apple-to-finally-bring-rcs-to-iphones/