Joe Belfiore has just tweeted that an updated version of the Facebook app for Windows Phone which supports Windows Phone 7 has just been submitted to the Windows Phone Store.
The app is expected to bring much of the improvements in the new Windows Phone 8 version to Windows Phone 7 handsets.
The app will bring faster performance, a new user interface, improved navigation, support for multiple resolutions and tile sizes, and more.
It should become available in a matter of hours to a few days.
Update: The Facebook Beta for WP7 is now available here.