The Eclipse project has implemented the Windows / WPF SWT since version 3.3. This does not mean something like XAML-Support or such things. It just provides a way to render a SWT widget using WPF instead of the Win32 API.
If you are looking for something like XAML, there is a project from Soyatec (eFace) that provides a XAML implementation on top of SWT.
e4 1.0 XWT, XML- SWT, . Databinding, Triggers .. . http://wiki.eclipse.org/E4/XWT.