If you recall, Microsoft showed off Tango in a stage video and HTC phones (Titan, Radar) are already loaded with Tango. Now, there are words that Tango will be available on Windows Phone from November.
The exact date might be 7th November 2011 and it seems that Microsoft has lend a helping hand to make the app better/smoothing. We are still waiting for the Skype app (no integration yet) which might also be ready in this year.
Anyway, enough of me ranting on Nokia Lumia 800. Looking forward to Tango for Windows Phone in November.