A five month wait from announcement to shipping might be plausible if this were the first Apple TV, but it's not. Such a delay following announcement would dry up sales of the current 3rd generation Apple TV, which would make no sense. It's called the Osborne Effect.
There is simply no reason to announce an update before it will be ready to ship. The Mac Pro was an exception because sales of the old model had already dried up and were actually banned in the EU.