It will be packaged with WordPress 3.5, which is slated to be released around early December.
It's probably called Twenty Twelve because (1) they're trying to be optimistic about the 3.5 release date and (2) the theme was meant to be included with 3.4, but didn't get done in time.
It's probably called Twenty Twelve because (1) they're trying to be optimistic about the 3.5 release date and (2) the theme was meant to be included with 3.4, but didn't get done in time.