From the info i have the Geforce 9 series was rushed in 2007.Expect the GT-200 to release sometime in 6-8 months.
Even the GT-200 appears to be a mildly powerful chip over the 9800X2 but its still early stage(so as they say).
BTW i am ready for some physics using multi-GPU,One of my systems is already installed with hybrid G84(8600GT) and G92(8800GT) GPUs,only the right software is required.