I don't know about LV specifically but I'm pretty sure at most shows, you place an order based on the looks you see on the runway or the "program" book as I call it. Some of the stuff designers will have stuff just for the show and not reproduce the item for sale. Many of them also have to "reinterpret" the clothes for street wear. The show is generally for editorial and very, very, VIPs (extremely wealthy = great paying customer or celebrity that gives them exposure). But yes, many times you can place an order before they hit the stores.