I\'m playing around with MVC 5 RC 1 in Visual Studio 2013 RC. Works very well.
Now I upgraded an existing MVC 4 project in VS 2012 to MVC 5 the same way as described
I got this answer from Microsoft developer:
MVC 5/Razor 3 tooling support for VS 2012 has not shipped yet. We hope to ship this support in Mid November.
So the accepted answer is true for now but we can plan to soon have this support in VS2012 as well.