One of two things can happen...

Either Apple does the bare minimum to implement RCS, continuing to make interoperability a pain in the ass. Meanwhile, keep making improvements to iMessage.

Or Apple does it right, fully implements RCS, contributes back to the standard, and abandons iMessage as maintaining two separate platforms for the same function is a waste of resources.

I'll take a guess as to which it'll be.

Alternatively Americans just accept using 3rd party messengers. But that field is huge with big and small names competing, and ultimately anything that displaces FB messenger or WhatsApp will just get bought by Meta (or some other FAANG) and we're back at square-one.

Everybody just remember that Apple is the stubborn ones here, reluctantly adopting the standard that every other OEM has been using for a decade, and the reason they've been doing this was as a means to keep people in Apple's walled garden by "othering" people who don't have iMessage.

They knew exactly what they were doing. I got rid of my iPhone to go back to Android literally a week after the original announcement. Exchanging multimedia with my wife was literally the only thing holding me to iOS. The alternative, using third party messengers, is just plain cumbersome for one user (and likely means selling your soul to Meta nowadays, anyway).

I doubt I'm alone.

And RCS is a neutral standard, belonging to GSMA. Even though Google is a key player, they aren't the only ones. Any phone OS or OEM could always have implemented RCS. Apple has historically chosen not to, while also not reciprocating the openness with iMessage.

I guess there is one other possibility...Apple embraces RCS and, being keenly aware of its limitations and with Apple and Android cooperating, they collaborate to develop a new open standard that fully replaces both. That's probably the best outcome but also least likely to happen.