Hopefully GT6 has online time trials, it adds so much lasting appeal to the game, trying to beat No.1 or some of your friends time. Why GT5 didn't have this I have no idea.
Not just online Time Trials. The game needs a robust leaderboard and class system. I'm a guy who loves running real GT racecars (LeMans, Super GT etc) and would be over the moon to get a game that had those cars classed properly with leaderboards where you could compete for top times and beating your friends.