At least with Google messages, you can still send normal SMS if your RCS chat can’t go through. I think there’s an option for it to automatically resend as SMS if RCS fails, too.

I guess there’s no way of knowing if SMS will eventually drop out of fashion, but it would be good to keep around so it probably will stay around as a back up

Edit: well, I didn’t see the other response say basically what I said, oops