They went silent because of the earthquake, tsunami and nuclear meltdown that have been affecting Japan for some time now. I think GT5 is probably the last of their concerns at the moment.
As for your question, I would hope that motorcycles are not going to be a part of the game. I'm a biker in RL but GT5 is about cars, not bikes. Best to keep a single focus, particularly as the game needs enough improvement as it is without introducing a whole new dimension. Save bikes for their own separate game.