Google announced that beginning on July 7 all Google Apps users will lose the ability to revert to the old Google Drive user interface.
The change from the old Google Drive user interface to the new UI will not impact the files you have saved in your account or how you go about using Docs, Sheets, Slides, and Forms. The change may impact where your files appear in your Google Drive dashboard and could change the way you sort some files. It took me a couple of a days to adjust. Since that initial adjustment period I haven't had any problems using the new Google Drive UI.