Looks like the new Docs and Sheets apps were harbingers of changes for Google Drive. The good folks at Android Police parsed Drive’s new, currently unreleased version and discovered that it no longer has document or sheet editing capabilities. Should you try to make changes, the app prompts you to download the appropriate app to do so. Choose not to download and attempt to open a file, and you’ll be greeted by a view-only mode. While users may be a bit miffed at being force-fed a pair of new apps, it may prove beneficial. Separating the doc editing and cloud storage components will (presumably) let Google streamline the experience for each and give you option to download only the apps you need.
Source: Android Police