This MSDN article refer to 3 flavors of Visual Studio Express 2012:
"This includes Visual Studio Express 2012 for Windows 8, Visual Studio Express 2012 for Windows Phone 7, and Visual Studio Express 2012 for Web."
UPDATE:
Windows Phone SDK 8.0 and Visual Studio Express 2012 for Windows Phone releases have been announced on Oct 30 2012 in the Build conference.