I agree with Uncle Meat, few Terminator owners are going to pay $20K over MSRP for a GT-500. They've lived through the markups some Terminator customers paid to be the first to have one only to see the last of them sell at big dicounts with even larger rebates.
Short term I doubt that there will be any effect on Terminator price. Possibly Terminator prices will rise for a short time as people who pass on paying big markups for GT-500s look for a used Terminator.
Long term, when GT-500 prices come down to sticker it may cause Terminator prices to drop a bit more than normal depreciation. But by then the Terminators will be 3 - 5 years old so I really doubt GT-500s will affect their prices.