The ideal transfer medium is the smartphone. It has Bluetooth and web connectivity, allowing phone-to-phone or phone-to-PC transactions, as well as wallet encryption and automatic backup. Also, eliminating the physical card helps people psychologically feel and understand that bitcoins are a step forward. Besides, one would be much more inclined to adopt Bitcoin if all it takes is downloading an app, rather than ordering a card.
You're right, an app is a great idea but I should be able not to do that if I want something to bring with me just to pay, a dedicated device. Freedom means being able to choose.