Google just announced that Apple will be adopting RCS in fall of 2024. If this is true, it's likely Apple is planning RCS adoption as part of iOS 18.
The Android developer just published an updated landing page for Google Messages, showing off key features ranging from customization, privacy and security, and, of course, AI.
On this landing page, there are different sections for each feature set, including one for RCS. As spotted by 9to5Google, if you expand this list of RCS features and scroll to the bottom, you see a section on "Coming soon on iOS: Better messaging for all." That's no surprise: We've known Apple was adopting RCS since November. However, it's the next line that brings the news: "Apple has announced it will be adopting RCS in the fall of 2024."
Of course, this does not say a lot as it is "in the fall" which is anywhere over a couple of months, and Google has tried to embarrass Apple into making moves before. I suppose, though, there is the looming court case against Apple which is anyway keeping pressure on Apple. If it were not for the US court case, I would have guessed Apple may have pulled out after the EU had ruled Apple was not a dominant player in the market (although the EU case was looking more at interoperability with WhatsApp and others in Apple Messages).
Of course, with Apple actually including RCS now, they can probably argue that there is interoperability via RCS between their platform and Android too. It must be remembered that in many countries, like mine, SMS's are paid for so are very expensive to use for any form of chatting, and the costs go up exponentially when you text an international number.
I personally have quite a few issues with interoperability with Apple:
I still have AirTags from when I had an iPhone and I daily get the audio beeps warning me the AirTags are not connected (I use an Android phone and alternate between an iPad and an Android tablet)
I can't wait to sell my AirTags and get the new one's Google was working on that will interoperate with Apple, but supposedly Apple has been delaying building in that support into their devices (which Google already built into Android for AirTags in 2023)
Because I was on Apple Messages and my iPad still sometimes connects, I find a message on my iPad that arrived a week ago which I had not seen (I had Beeper which was solving this problem)
Apple is not at all dominant outside the USA, but it makes interacting with Apple users quite a pain, as Apple has gone out of their way to try to keep their users inside the walled garden.
It will be when SMS s phased out. That was why it has been a long, uphill battle to get the mobile phone providers to buy in. That has to happen before SMS can disappear. That is why no other "messenger/chat apps" need mobile provider buy-in. RCS happens at carrier level, and not as an installable 3rd party app. It's exactly why it will be adopted by everyone as it is designed to replace SMS.
There is no need for carrier based messaging anyway. It's like with fax machines, sure there can be new Internet based protocol for fax machines that phone/fax carriers would start to support and new printers being forced to adopt, but if it's Internet based why not just use email.
At least SMS is using voice PSTN network and is purely device-to-device, so it can stay for emergencies. But RCS is purelt Internet based messenging that was abandoned because of no benefit over what we already have like XMPP, until Google started forcing it. Right now Google Messages are the only RCS app on the market and the only one available to support it, because carriers just delegate servers to Google for hosting.
RCS is carrier based though, which is why the carriers had to buy into it, and they turn it on, not Google. Many in 3rd World countries don't have e-mail. Many legal notices are today still sent out by text SMS. I get them all the time for bank transactions, government notices, etc. Actually, Samsung's Message app also supports RCS, and this is what Apple is building into their Apple Messages app too.
Both Samsung and Apple are doing it with tight cooperation with Google. Most carriers are using Google Jibe service for their RCS servers.
It is in fact carrier based at the fundamentals, it's true. But it still is passed trough regular IP network and in practice there is nothing special in RCS compared to internet standards like XMPP other than connection with phone number being required instead of optional.
The GSMA does need to work harder at ensuring true interoperability between carriers, esp for E2EE. I'm expecting that the Google "monopoly" will get broken up at some point. I would have hoped that Apple insisted on hosting their own RCS (standards compliant) server.