Visual Studio 15 Preview is the latest version of Visual Studio, which is expected to be released this year. I am sure the final product name will be Visual Studio 2016, based on previous names.
Today, to install all features of this Visual Studio, you will need 36GB space on your machine. See the following image.
You may want to uncheck the features that may not interest you.
Visual Studio 15 Preview ships with C# 7.0. To learn more about the preview and what is new in it, start with