They were tweeted just before announcing the blackout. My guess is that when the blackout happened they tweeted the pre-comitment as soon as they could just in

They were tweeted just before announcing the blackout. My guess is that when the blackout happened they tweeted the pre-comitment as soon as they could just in case. They are not the keys because nothing that terrible happened yet. All they say is that they have files on those topics, and if someone in the future releases keys to some files, and those decrypted files' signature is as it says on the tweet, then they must come from Wikileaks, since they posted that signature.