I do think that one key difference between Britain an France is that Britons had plenty of obvious destinations to go to, while a France that was not that much poorer did not. With New France lost, the only option were relatively unattractive, like an Algeria that ended up attracting a mostly non-French population of colonists or a Southern Cone that was distant (and particularly popular only among people on the Pyrenean margin with their Spanish connections). If you did have at least one Francophone country of note—a thriving Canadian republic, say, or at least a Canadian state in the US—I think you could have had a big exodus.
