I drink Starbucks daily. I would love to see this. I can't imagine using Bitcoin in a scenario like this. If this happens and other retail outlets are forced to compete Bitcoin will be accept around the world almost instantly. Very exciting. I hope it happen soon.
This is one of the reason why Starbucks will come up to the acceptance of Cryptocurrency in which people of nowadays were very conduxtive regarding whaf is Bitcoin all about and if this will happened I think many customers will purchased their products and the more that they have engaged to change the more they will be inline to the well known entities who risk to try Bitcoin transactions.