Read about this recently. Read more here http://www.computerworld.com/softwaretopics/os/story/0,10801,95538,00.html?nas=PM-95538.
But WinFS will be available with the client version of LongHorn when it is released. I suppose keeping the deliverables to the limit, we would get some real working, secure and robust components of LongHorn. Over promising with the deliverables would cause lots of features but with lots of compatibility issues and BUGS!
Information on LongHorn here -- > http://msdn.microsoft.com/Longhorn/understanding/