It'll either be an announcement for pre-orders, or that the machine is shipping now.
With the problems the 970fx has been having -- who knows.
But there are hints of two machines right now.
Looking like our Rev. B machine (aka Speed bump 970Fx), and the possibility of a machine using a new chipset.
The possibility of the new chipset can be either the next generation PPC9xx with PCIe/DDR2/etc., or a PPC970 capable consumer chipset.