For a moment I got all excited and thought they had ported WPF to OS/X.
I get the impression that WPF is pretty much on life support.
The developers that have still not abandoned WinForms will not jump shit when the next thing hits either. To keep the huge group of WinForms developers happy, Microsoft will continue to support and develop Winforms. For many, WinForms are still the fasted way to develop simple applications.
So if you want develop for the Windows (desktop) platform, WinForms will be a clear winner for many many years into the future.