I fly Air Canada to Orlando from Toronto in a couple weeks… based on the seat selection my flight is 90% full.. but the Westjet flight that got cancelled on me last week causing me to rebook was only about half booked based on the seat selection
I would say most Canadians plan their WDW trips well in advance (6 months to a year?) and so I wouldn't expect to see softening flight loads for a few months yet. With that said, there's already concrete data that in general, travel to the US is dropping: https://www.cbc.ca/news/politics/cross-border-trips-decline-235k-february-1.7485695