The trick is to sell tickets based on the cost at time of sale, and just cancel flights when it's convenient.
It doesn’t work that way. Canceling flights has significant business-impacting downstream effects that go beyond mitigating the loss caused by a bad bet.
When airlines cancel flights, they usually put you on a similar itinerary, not just refund your money and hope you rebook at a higher price.
That said, I don't know a lot of people that book that far in advance, even when their travel plans are well settled.