"We're sorry to disappoint customers waiting for the white iPhone again," said Apple spokeswoman Trudy Muller. She declined to explain the delay.
Apple has never explained what the specific delay with the device has been. They've only said it has been "more challenging to manufacture than we originally expected."
A recent update to the Apple Store app which allowed for reservations of the white iPhone had given hope that the device would be available before Christmas; however, according to Apple this is not the case.