It's going to be irrelevant. It will still be separate from iMessage. Different bubbles will still exist. People who aren't using SMS now (Europe) will continue to not use RCS either. And Apple's implementation of RCS will be independent from Goggle's and not 100% compatible.
In fact I suspect the whole thing is an attempt to skirt the upcoming EU interconnection regulations. Apple thinks that if they say "look we've implemented RCS and it's technically interoperable with other RCS implementations" they'll get a pass — or be able to assign blame on other vendors for not interconnecting with them and drag the whole thing for a few more years.