I believe Western Australia held a referendum on independence during the 1930s. The Yes side won. They sent a delegation to London to try to secure some recognition but didn’t get anything out of it. We don’t really hear about it today, even though Western Australians still feel somewhat alienated from the rest of the country.
I’m bringing this up because the fact is that a group of people, even a national community, doesn’t have any inherent right to declare that they are an independent country. International law tends to favour the territorial integrity of existing countries. A new country needs to find some international recognition, and this isn’t always easy, especially for a country unilateraly separating from another one.
Of course, if a majority of Quebecers ever vote Yes in a referendum on independence, the rest of Canada should find it a good idea not to ignore it. Depending on the leaders in place on both sides, we should expect bilateral negotiations to take place.