The documents remain available to share and download. If you have exceeded the free 5 GB storage limit, you cannot add any further documents. You can access and edit your documents that are saved on OneDrive using Office Web Apps. You can save your OneDrive documents to another computer or disk drive at any time.
Essentially this means at the end of your subscription period you revert from 1 TB to 5 GB storage. They do not delete your files even if they are more than 5 GB. However, you cannot add files until you bring the amount down to under 5 GB by saving your documents elsewhere.