With the Windows 10 Anniversary Update, Microsoft introduced the new Desktop App Converter (aka Project Centennial) in Windows 10. The Desktop App Converter allowed developers of the classic Win32 apps to bring their apps to the Windows Store and take advantage of some modern Windows 10 features such as Live Tiles and the Action Center.
Full Office apps in the Windows Store were first spotted back in February 2016. Microsoft is now planning to officially release the full Office apps via the Desktop App Converter in Windows 10. The full Office apps will be available sometime around April 2017 which is when Microsoft plans to release the Creators Update for Windows 10 devices.