The updated OneDrive roadmap for the first and second quarter of 2017 suggests that Microsoft plans to add differential sync support to OneDrive in the second quarter of 2017.
Microsoft revealed back in 2016 that it had plans to introduce differential sync support on OneDrive. The company listed the feature under committed, but did not reveal a timeline back then. This meant that it was not clear when Microsoft would introduce the feature for all files, but that it was working on it.
Microsoft customers suggested as early as 2014 that Microsoft should introduce differential synchronization