I am working with Visual Studio 2010 - SP1
I installed ASP.NET MVC 4.0 RC on my box. The option "Use HTML5 semantic markup" is missing in all the project templates (empty application, Web Api, Internet app, Intranet App) when creating a new project of ASP.NET MVC 4.0 Web Application project type.
Remember, I have not installed asp.net mvc 4 beta prior to RC installation. However, this option is present when creating an asp.net mvc 3.0 web application.