During his OSCON 2007 talk, Steve does say that "NBL" is JavaScript 2. Watch http://blip.tv/file/319044/ around the 24:40m mark.
Then again, I don't know what's his opinion at press-time.
Is it possible to do anything with that apart from run the existing Smokescreen demos? There's nothing on the site that refers to anything having shipped or even a target ship date.