I'm under the impression that Android devices have had optional full disk encryption[0] for a long time, and that encryption isn't dependent upon cloud synchronization.
Having said that, high-end devices [1] from Marshmallow onward (6.0+) are supposed to have encryption enabled by default, according to the Android Compatibility Definition Document [2] so we'll probably see Android playing a bigger role in the encryption debate in the future. Budget phones are exempt from the requirement.
[1] - For device implementations supporting full-disk encryption and with Advanced Encryption Standard (AES) crypto performance above 50MiB/sec
[2] - http://static.googleusercontent.com/media/source.android.com... Full Disk Encryption (section 9.9)