bitflipper,
I had done some work using the Alesis iO Dock and it has a coupl eof phantom powered inputs.
Also I tried using my PreSonus AudioBox VSL22 and again only two mic inputs.
The thing about the iPad's is the class compliant USB architecture. This is accomplished through the camera connection kit. You also need to use a powered USB hub to connect the USB audio interface and depending on the number of inputs the interface has that will be what shows up in the DAW. This I know for a fact is true in my experience using Harmonic Dog's Multitrack DAW App.
It will be interesting to see exactly how far they can really push it.