For all the developers who are already working with VS 2012 or thinking about it, here is an article on the projects and project types that it can support. The following article is a summary from the msdn article (Visual Studio 2012 Compatibility)
One of the major features in the latest release of VS is that you can work with Visual Studio 2010 SP1 projects and files in both Visual Studio 2012 and Visual Studio 2010 SP1. So, if you created your assets in VS 2010 with Service Pack 1 (SP1), many of them will load and run in VS 2012 without any further action on your part. Many assets will also open again in VS 2010 with SP1 without any issues, even after you open those assets in VS 2012, due to its enhanced backward-compatibility.
But you might need to upgrade certain types of solutions, projects, files, or other assets that you have created in previous versions of Visual Studio (2008 and below). Below is a summary of the compatible and incompatible assets.
Automatically compatible assets
The following table lists the project types, file types, and technologies that work in Visual Studio 2012 with no additional modifications or effort on your part.
You can open all of the below listed assets in both Visual Studio 2012 and Visual Studio 2010 with SP1 and, and it will behave the same way, no matter which version you’re using. For example, you can use Visual Studio 2012 to open and modify a project that was created in Visual Studio 2010 with SP1. If you then reopen the project in Visual Studio 2010 with SP1, your modifications will persist, and the project will continue to behave as it did in Visual Studio 2012.
Some assets that were created in Visual Studio 2010 with SP1 require modification to open in Visual Studio 2012. If you open an asset that requires modification, the Review Project and Solution Changes dialog box appears and categorizes the asset into one of the following groups: