It doesn't need to be "turned" into a general purpose device. It already is. That's its nature. It's Apple who turned it into an "appliance" by artificially limiting what programs you can run on it. It quite literally is a general purpose computer that can run any program except the ones Apple doesn't like.
This is merely child's play, by the way. The future will no doubt feature governments wanting in on that action. Computers are subversive, after all. Encryption alone can make a mockery out of police and courts. They absolutely love the concept of a computer that runs only software that doesn't harm them.