If I say that there's no guarantee that everything will be ready at launch, I'm saying that at some point this "everything" will be ready.
I don't think that says that at all. I think it implies they intend that some will be ready at launch, and they intend that a good portion of the rest (but not necessarily all) will be ready at some point after launch, but it by no means excludes the possibility that some will never be ready.
In fact, at the very end of the article he directly says they probably won't be:
Mike Mearls said:It's a big list, and probably more than we can fit into what we hope to provide. At the end of the day, the advanced rules are likely to be more of an ethos or an attitude that casts the DM as a game designer who can alter the mechanics or add to them to suit the specific needs of a campaign.
I think he makes very clear that the list is aspirational and not promissory.