Not only is the Tesla Model S in Gran Turismo 6, but it is featured prominently in trailers. Pretty amazing that they picked 4 cars for this trailer and one is the Model S:
Pre-Order - PRODUCTS - gran-turismo.com
Gran Turismo 6 Pre-Order Trailer (US) - YouTube
Pre-Order - PRODUCTS - gran-turismo.com
Gran Turismo 6 Pre-Order Trailer (US) - YouTube