Explanation of the AT&T Order Status Screen
When your status reads PROCESSING and not BACKORDER, it means that your order number has been paired to an iPhone S/N, it will be shipped in the first batch, and you will likely receive it tomorrow.
If it does say BACKORDER, it means that they received the order, and they anticipate enough stock for the 2nd or 3rd wave, but they have not paired your order number to the S/N of a phone (and this changes day to day) - so if it says BACKORDER now, it might not later today or early tomorrow.
The long and short of it seems to be, if it says PROCESSING you're going to get the phone on launch day. If it says BACKORDER, there is still a chance it will come on launch day.
Hope this helps!
What does Shipped mean?