It not a leak, it's marketing in the same way that politicians release copies of their speeches to the press the day before, so that the press can prepare their coverage - while it's still current news not yesterday's. This "leak" and the speculation about what it contains has put Apple squarely back in the headlines, just as it's going to release a new phone model and other stuff. The press are lapping it up and it's costing Apple nothing.
Without this hype, Tuesday's announcements would have been relegated to the unread backwaters of the tech sections of the press.
Bang on.