Starbucks is not only one of them most popular brick and mortar coffee shops, but now with a smartphone app, they are sure to dominate even more. To make it even more convenient to access Starbucks and their products via the app, will just increase sales and popularity of the brand.
The history of the last half century or so of changes in consumer culture have shown that the appetite of the average consumer for greater convenience is virtually bottomless. While walking up to a register and placing your order in person may not seem like a great inconvenience, the ability to avoid this procedure and thereby quicken the process of ordering will very likely encourage sales in moments and situations where a consumer might otherwise choose to forego the purchase.
Starbucks has conditioned their customers to want the very best. A new app that has your latte waiting when you arrive, on the service seems great, but in the long run will not increase sales. Customers will expect their latte to be freshly made, and when they order ahead they will not know how long their drink has been sitting. This will likely increase the number of unhappy customers, and the number of drinks that end up having to be remade. Also, the two main types of customers are repeat, everyday customers and spur of the moment customers. Everyday customers will come whether there is an app or not, having no effect on sales. Spur of the moment customers will not be interested in ordering ahead and will instead want to wait and decide what to order in the moment.
People are willing to wait a long time as it is for their Starbucks fix so I do not think it will increase sales too much. What it will do is decrease wait times and get potentially happier customers. Starbucks is such a dynamic brand that I don't think they will gain a whole lot of customers from this. The people that are currently not going to Starbucks, don't go there because the line is long. They avoid it because they either don't like the coffee or they don't like the big national brand. This app won't change any of these peoples attitudes.