last launch I have any physical experience with was iPhone 4. I got to Pacific Centre in Vancouver at 6am on day of launch and the lineup was about 400 people deep. The guys at the front had been lined up for about 24 hours
I remember being in that line. Good times. Absolutely awful exp in some ways but even with that huge line I came out with a phone.
iPhone lines tend to be much harsher than iPad lines, in my experience. In Montreal last year I showed up a little under an hour early, was maybe 20 people back, but the Apple Store folks were super organized; they basically came to every person in line, gave a card verifying the color/capacity wanted, and registered it on their work iPhone. Then they followed that up with the free coffee and snacks cart. Virtually every person in line knew that they were going to get what was on the card, and once they were "open" the line moved ridiculously fast.
I'd love to believe those factors carry over to the phone launch, but, by comparison, I don't think that Apple Store had any 5S stock that day. Ridiculous fees just don't seem to get in the way of people buying the phones first. So I really wouldn't be surprised if 6+ stock in the main stores is extremely, PS3 style limited.