Apple have never missed a product launch. Products are normally in stores the day Steve announces them. The iPhone was an exception because of the FCC regulation. So there is no track record of missed launches.
Apple have not said they will only make 10 million iPhones. They have said that 10 million units is their target. I am fairly confident that once they sell those, they will be making some more. In fact, I daresay they will ramp up manufacturing if they see that iPhones are selling out more quickly than expected. This is because they are not morons.