Refer to the OneDrive changes that the OneDrive Team had announced in a blog post here.
The free tier will see its storage drop from 15GB to 5GB. This is applicable for all users. The 15GB camera roll storage bonus will also be discontinued. All these changes will start rolling out in early 2016. If you’re using more than 5GB, you will continue to have access to all files for at least 12 months after these changes go into effect in early 2016.
To let existing OneDrive users who have 15GB of free cloud storage and 15GB of camera roll storage to keep them, you need to sign in to your Microsoft account and opt in at this page.