Microsoft has announced that the amount of cloud storage available to free OneDrive users will be reduced from 15 GB to 5 GB on July 27th 2016. Users who have exceeded the quota will be notified to move the data or upgrade to a paid plan. After 90 days, the data over 5 GB will be made read-only for 9 months. After 9 months, the entire OneDrive storage will be locked, and will be deleted after one year with no user response.
Office 365 users with unlimited storage will now be limited to 1 terabyte of data.
More information is at https://blog.onedrive.com/onedrive_changes_FAQ/.