iOS 8 has, and the next Android L will have, encryption of user data on device level as default. Android have provided this as an option for a while. iOS as well, but with decryption keys accessible outside the device.
FBI and more fedreral agencies are worried this will hinder them to fight terrorists and other criminals. A request of information letter will not longer help government agencies much.
From the privacy perspective, it will provide us honest and low-abiding with the privacy we want and need(?).
Bear in mind that cloud storage and backup is not covered by this, and that personal info is shared by apps when the phone is in use. Producer back-doors etc. is a totally different story…