As long as the flight is still showing in the system, AC cannot rebook you. I was booked on a HKG-YVR flight back in March that was showing all zeros for the coming months as they were planning to reduce to 1 flight a day back then. I called the SE desk and asked them to put me on the other one so I could keep my upgrade but they insist that as long as they see that the flight is not "CANCELLED", they can't change it without charging a change fee. So I think you will have to wait til AC's system being updated being they will change it for you. Of course, you could try and call them and tell them that you've heard about this flight being cancelled.