Visual Studio 11 Beta is ready for you. Now you can download it from browsing http://www.microsoft.com/visualstudio/11/en-us/downloads and also can download from MSDN Subscriber Downloads .
There are some compatibility with previous releases. I think the main points are,
- .NET 4.5 is an in-place update of .NET 4
- You can install and Use Visual Studio 11 Beta alongside Visual Studio 2010.
Also, there are some upgrade paths planned ready for Developer Preview / Beta / RC / RTM later on.
- Upgrade from .NET 4.5 Developer Preview to Beta
- Upgrade from .NET 4.5 Beta to Release (RTM)
- Upgrade from VS11 Beta & .NET 4.5 Beta to RC
- Upgrade from VS 11 RC & .NET 4.5 RC to RTM
- Not Supported
- Upgrade from VS 11 Developer Preview to Beta
- Upgrade from VS 11 Beta to RTM
Because the download available now is the Beta already. So the installation are ready for you to upgrade from Beta to RC only. You may have to uninstall it and install RC. But once RC is ready and after you installed RC. You could direct upgrade from RC to RTM.