I HIGHLY doubt that the updated minis will get such a GPU. It doesnt make sense for Apple to throw in a far superior GPU than even what the higher end Macbook Pros are equipped with.
I have a strong feeling it'll be the same gpu as the lower end 13" macbook pro (most likely the nvidia 320GT).
I wouldnt mind an nvidia 320GT on the Mac Mini, that would be a dramatic upgrade for the Mini.
99.9% it will be the 320M