The best thing MS could do at this point is drop non-Kinect SKU's and drop the price of Kinect SKU's to $199 & $299 respectively ($100 pricecut)
But in the event that doesn't happen (which I think it might actually happen) the prices will most likely be as follows
4GB SKU = $149
250GB SKU = $239
4GB Kinect SKU = $239
250GB Kinect SKU = $339







