Kazunori Yamauchi gave some pleasing details today on his twitter account on what the Gran Turismo 5 Spec 2.0 update will include.
Kazunori Yamauchi is continuing to give information. we're updating the post as he does. He seems not to be done yet too.
Second update: Yamauchi also specified what they have in store for DLCs
Third update: Post updated with release date (october the 11th) and official screenshots.