The Verizon iPhone had no lines at all really. I would say this is gonna be a bigger line than the first iPad launch actually, or at least somewhere equal to that. Plus the 1st iPad launch had two launches (one for Wi-Fi and one for 3G), this time there is only one launch. Remember that there is no contract to sign here, and the price ($499) is in the perfect impulse buy range for a lot of people.
But to answer the OP's question, I doubt every store will sell out, but the 16GB models will definitely go first. I think one of those stores is bound to have some of them even 12-24 hours after launch. Some stores will sell out, but some stores won't. Something to remember though is that the Apple store always gets the most units in stock.