What do you think are the chances to see a turbo charged 3.0 in a 4th gen? If I'm not mistaken it has 3 more years to live before the 5th gen is introduced.

 

This will only happen if the GS follows the LS path and gets the 4.5 gen face lift. It is however, highly unlikely that gen 4 will get anymore updates from Lexus. By this time, Lexus engineers are already working hard on the 5GS.