There's no official announcement from Microsoft -- at least so far -- but the company seems to have made Microsoft Office available to all Chromebook users.
That discovery is courtesy of "Chrome Unboxed," which reported on November 22 that users of various Chromebook models were downloading the Office apps from the Google Play Store.
In 2014, Microsoft made the web versions of its Office apps (Word, Excel, PowerPoint, and OneNote) available to Chromebook users. Subsequently, Microsoft made Office Mobile for Android available, and those Office apps worked on Chrome OS devices.
While users of some Chromebook models from various manufacturers previously reported they could get Microsoft Office from the beta of the Play Store, the apps were not generally available to all.
Microsoft officials told Chrome Unboxed last year that Microsoft was working with Google "to deliver the best experience for Chromebook users" and planned to make full Android versions of the Office apps available on all "compatible" devices by the time the Google Play Store on Chrome OS was no longer in beta. But since that time, Microsoft execs had not provided an update on when Office would be generally available on Chromebooks. In the interim, some have been using CrossOver to run Windows apps on their Chromebooks.
I've reached out to Microsoft for more specifics on Office on Chromebook availability, but no word back so far. Microsoft makes Office apps available for free to Android tablet users with devices with screens under 10.1 inches, but requires those with larger devices to have an Office 365 subscription to use these apps.
Update (November 30): Microsoft officials mentioned in passing the company's Office on Chromebook support in a blog post summarizing Office-related announcements for the month of November. Microsoft is categorizing the Office Mobile apps on Android (Word, Excel, PowerPoint, Outlook and OneNote) for Chromebooks as a "preview." From that post:
"Office Mobile apps on Chromebook--Earlier this week, we released a preview of the Office Mobile apps for Google Chromebooks. These apps were originally designed for Android phones, and they're not yet fully optimized for the Chromebook form factor. We've done some initial work on the end user experience and want to gather customer feedback. As with all of our mobile apps, an Office 365 subscription is required to edit documents on devices with a screen size of 10.1 inches or greater."
Microsoft is positioning its Windows 10 S operating system, which runs Microsoft Store apps only, as an alternative to Chrome OS.