Tango - the next Windows Phone version - will be announced and launched at the upcoming CES 2012 in Las Vegas. It will be demonstrated on the still unannounced Nokia Lumia 719 and Lumia 900 on January 13.
The Tango update is supposed to bring LTE support and smaller resolution displays compatibility.
Furthermore, Windows Phone Apollo - the next major Windows release (codenamed Windows Phone 8), will be announced and launched in mid-June 2012 at the Nokia Connection 2012. The Apollo will bring support for dual-core processors, high-res displays and NFC. It might do some changes on the UI, too.
We should be also getting multiple hi-end Nokia gadgets at the Nokia Connection 2012 including the long-rumored successor of the camera-centric N8 and Nokia's first Windows 8-based tablet.
All this spicy info was revealed to DGui from an industry insider, but you should still take it with a pinch of salt.