Coinbase is covering their ass because of the Bitcoin Cash fiasco. They're basically saying, "We're not adding anything until we add something. And when we do, it will be officially announced."
i.e. they're not just going to suddenly add it and then tell everyone like with BCH.
Will that really make a difference? Some amount of people is still going to know about the announcement in advance. The only difference is that Coinbase might actually have the resources to scale the release this time if they track how big of a deal their announcement is.
i.e. they're not just going to suddenly add it and then tell everyone like with BCH.