With 2.6 release, NuGet Installer is getting split into two. This allows NuGet to use Visual Studio 2013 specific assemblies to provide the best NuGet experience in Visual Studio 2013. This also allows NuGet extension to have a smaller footprint and enables to use Visual Studio version specific optimizations.

Starting with 2.6, we will build 2 VSIX as below:
1.NuGet Package Manager for Visual Studio 2010 and Visual Studio 2012
2.NuGet Package Manager for Visual Studio 2013

We can also add links to the CodePlex download page from here