Where did I read what? I'll assume you mean that Apple TV units are getting shipped today? I live in Australia, there are plenty of people here who got shipping notifications yesterday to say their items have shipped for delivery today (Friday).
One would assume that Apple will have the back end live by the time the units are delivered otherwise they will receive support calls from each and every non technical end user wondering why their units are "broken" and missing the app store etc. because Apple haven't put the back end live.
The App Store is already on the device. How do I know? Pick an app that already exists on your development Apple TV, and ask Siri to start, run or launch it (I can't remember exactly what I said). The app will launch. If you try launching an app that doesn't exist, Siri will say that it can't find it - an error message. However, if you try and launch the App Store, Siri will try but will say it can't launch it - implying that the app is already there and it found it, but it can't launch it.