We will continue to fully support .NET 4, 4.5, 4.5.1, and 4.5.2 until January 12, 2016, this includes security updates as well as non-security technical support and hotfixes. Beginning January 12, 2016 only .NET Framework 4.5.2 will continue receiving technical support and security updates. There is no change to the support timelines for any other .NET Framework version, including .NET 3.5 SP1, which will continue to be supported for the duration of the operating system lifecycle.La nota semioficial de Microsoft se puede leer en el blog .NET Framework. Por si no lo había notado:
The quick pace at which we’re evolving and shipping means the latest fixes, features, and innovations are available in the latest version and not in legacy versions. To that end, we are making it easier than ever before for customers to stay current on the .NET Framework 4.x family of products with highly compatible, in-place updates for the .NET 4.x family.