It depends on the store, but it's possible.
I was there today, and the woman I know who works there told me that they had just gotten 10 boxes. That didn't include the 30 or so preorders, I don't think.
BTW, she also told me that last year, the line started forming at 3:30 am, and when she got there at 6:30 for a 7am open, the line was down the block. So I wouldn't say showing up at 7 gives you the best chance.