Do you agree that French should be the common language in Quebec?
There can't be two common languages. Basically, the flaw in this reasoning, in my opinion, is the assumption that languages are in competition with one another. You can't deny it. The more French gains ground, the more English loses ground. If everyone were bilingual, the choice would always fall on the majority language. As long as we're in Canada and North America, the majority language is English.
It's normal for newcomers to gravitate toward English, since it's the language of the majority. Even in Quebec, that's how it's perceived. Federal institutions do operate primarily in English. We've heard all kinds of testimony on this. Federal institutions and public services are the places where people work the least in French.