DVC has not announced when sales will begin. The villas are still scheduled to open in late 2009, so it will be sometime in the next 9 mos or so.
If DVC follows past practices, points bookings at the Grand Californian will end when the villas open. They won't even let you book dates after the projected villa opening. For 2010 the only option for the Grand Californian would be to secure one of the DVC rooms.