You couldn't be more wrong about Apple. Jobs was ruthless toward anyone caught leaking, suppliers and employees alike. Not only would you get yourself fired, you'd get your ass sued off too.
Jobs was the master of startling the audience with unexpected surprises and is what made Apple launches such a must-watch event.
That magic has been lost in the Cook era. Now there is no point in watching launches because everyone knows everything ahead of time. But without a doubt, Apple doesn't leak anything on purpose. The company is just too big to keep secrets now. But most of the leaks only come out weeks before the launch while Apple is often working on secret projects two years from production. (well, there is some speculation they leaked the headphone jack thing so it wouldn't distract from the product announcement.)