The next version of Windows Phone called Tango seems to available for some smartphones. With build number 8773, the Tango update has arrived for Nokia Lumia 710 smartphone bundled by T-Mobile. If you see on Microsoft website, the Tango update for that smartphone will come soon.
Some time ago, Microsoft also revealed the newest version of Windows Phone update page. The page shows 7.10.8773.98. OS. It is supported by Microsoft Spain website that Windows Tango update is available and ready to be installed on compatible devices.
Unfortunately, the site says that the update is not for all countries and languages. Maybe, Spain has got this update and will be followed by another countries.