The concept of a drone delivering parts is plausible. I think they are showing the Phantom for example purposes.
Of course, it will require a beefier drone to carry packages. But I think a key feature that is missing today is collision avoidance technology. Today, our drones are dumb. They either require us to maneuver them line of sight or FPV. But in RTH mode, the drone will simply fly into trees, buildings, power lines, etc if those objects are in the return home path. The only way you can safely negotiate variable settings for commercial use, i.e. delivering packages, is for the drone to have awareness intelligence. My guess is that this technology is not far away (you're starting to see it in higher end cars) and will not only change our hobby greatly, but make commercial delivery applications possible. Image your Phantom having the ability to automatically take over the controls to steer the craft around an immanent building impact. Or automatically avoid a curious child that interferes with the delivery process. Can't wait for... 'one day.'