I think people will come flooding back to GT6 when/If the Course maker is added. The none presences of the course maker, is the Only reason people have stopped playing.
It will only last a couple of weeks though. People will come back, grab their updates, try the course maker then ditch the game as we all realise the course maker hasn't made a significant improvement over gt6's lack lusture everywhere else in the game. Again growing bored of it very quickly as we continue chasing that feeling that not there.