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
For me, my issue was that I had my build files being output to a directory other than bin. Once my files we're output to bin, then my syntax highlighting came back.
One way to fix this is to create a post-build action which copies the files in the project-rooted bin folder (vs a filter outside of the project) to your target directory.
The following article explains: http://www.dennisonpro.info/managing-intellisense-in-razor-views-with-mvc-5-using-custom-builds-in-visual-studio-2013/