More gesturing and intuitive human interfaces seem like a good guess -- with the iPhone, the accelerometer has been used in all sorts of interesting ways, and it's probably not far until Apple figures out a way to track movement in 3D space, either by moving an iPhone or a controller around, or as the piece suggests, by tracking our body in some way. Slimmer display screens and extra battery life will be in the future as well. And the article mentions solid state storage, but if our predictions for this year are any indication, Apple will try to move off the hard drive as much as possible, and start placing data for multimedia and other files in a cloud server, accessible via Internet whenever they're needed.
Like I said, interesting thought experiment. What do you think Apple will be like ten years from now?