I honestly feel that there will be a very (and I mean very) limited stock on hand on launch day for those who want to queue up, but they're not going to announce that publicly. After all, it's the new head of retail Angela Ahrendts that was trying to avoid the "whole camping out in front of a luxury store" thing in the first place.
To me, it actually doesn't make sense that they wouldn't have any inventory whatsoever on launch day. If they could make a very small surprised few customers happy to supply one - if it so happens to be the exact version they're looking for - they would certainly do it for the positive customer experience. And, I'm sure that people who get offered to buy that one available model will most certainly not turn the offer down.
I was lucky enough to preorder my iPhone 6 Plus, but when I walked into an Apple Store a day after launch day and they lines were out the door, they allowed me to skip the line and walk right in when I told them I already preordered, but was just looking for accessories. While purchasing an iPhone 6 Plus, I was with my daughter and told them that she's going to probably get one in the future, but the backorder was about a month, the store rep said, "Oh, we do have a select few in stock, want one?" I turned and looked at the long line out the door waiting to buy one, and said, "Yeah, of course!" and I was out the door with a second one.