Microsoft's Office is already available on Android—but only for phones. According to The Verge, Microsoft is now developing a version of Office tailored specifically for Android tablets, and the company is gearing up for a private beta program.
That news comes from "sources familiar with Microsoft's plans," who told The Verge that Microsoft is already letting people sign up for the beta through this page on the SharePoint website. Both home and business users are welcome, although the page doesn't explicitly say anything about Office for Android. It simply notes that the Office team is looking for users to test "pre-release beta programs." For all we know, you could be signing up to try a Clippy plug-in for Office 2013.
The Verge says the tablet-friendly version of Office for Android will come out "later this year," apparently before the Modern UI release for Windows, which the site says is "currently scheduled for early 2015." As a reminder, Office for iOS (both phone and tablet) has been out since March. If I didn't know any better, I'd think Microsoft cares as little about Modern UI as the rest of us do.