A British loss just keeps the colonies tied to Great Britain longer. When the next war rolls around the population disparity in North America will only be greater. The French can't hold out there forever.
I kind of have the opposite view. The British needed to take Canada while its population base was still small, which they did. If they'd needed to wait 30-40 years, that population wouldn't be so small anymore, because the French-Canadian baby boom (which would last over 200 years) had begun. French Canada was characterized by an unbelievably high birthrate for a long time. The population of French Canada tripled between 1720 and 1760 (from 25,000 to 75,000) and it continued to grow at that rate for two centuries. (Quebec's population was 1.1 million in 1860, and 5.3 million in 1960. Throughout this time, French Canadians made up 80-85% of the population, despite receiving almost no immigrants from French-speaking countries.)
Now of course, the population of American colonies would still greatly outnumber Canada's population in the event of any future war, but when you have hundreds of thousands of people on your side, as opposed to 75,000, you can withstand a lot more losses and keep fighting. A British invasion in 1800 would face a better-manned Louisbourg and Quebec City, and in the event of victory might then have to take on Canadien guerillas - to say nothing of the Native Americans. (As it was, in OTL the British had their hands full with Pontiac's rebellion.)