The announced open-sourcing of several libraries such as WPF or XAML won't make developers use them more. Microsoft would like developers to forget their original sin, which is to stop supporting libraries randomly after some time and for no sound reason. Developers are better off sticking to WIN32, should they have to write native Windows applications, because that's the only stable thing, and that's provable. Of course, suffice to say that the last ten years, Microsoft has made life miserable for developers when it comes the time to deploy and sell software because of the gratuituous warnings bombarded to customers for daring to install foreign software, and false flags from anti-virus software including Microsoft's own anti-virus software.