>There is a case for a strong cross-platform messaging app, but RCS isn't it. And whatever it is, it needs to be at least as good as iMessage or iMessage people won't use it.

I think the case should be more for basic interoperability like the EU is doing. That's why iMessage is such a default on Apple's devices, basic interoperability with SMS. There would be a lot less people on iMessage if it was a separate app than SMS. Plenty of people would rather have a single app with good enough features, but can message everyone under the sun (SMS is not good enough). Similar to Pidgin and Trillian which had less features than using AIM or MSN Messenger directly back in the day.