Why wait until after travel. You may have an argument supporting being able to obtain a refund of the cancelled segment, but if you wait, AC will surely reprice the ticket for what you did fly and that may approach the cost of the existing ticket.
If your flight is cancelled, you are entitled to cancel and ask AC to preserve onwards segments. You are not then flying "out of sequence".
How do you propose to get to your destination so that you can fly home?