I kinda hope they don't buy out Fiat. The Germans do "efficiency" and "built for purpose" very well, but generally don't have the character of the Italians (perhaps excepting AMG and Porsche). Plus having Ferrari and Lambo in the same stable is not good for either brand.
Then again, it would be better to have Fiat, Ferrari and Maserati under the VAG umbrella than not have them at all.