First of all, I believe that immigration raises a problem that no one has mentioned, the possibility of a perverse impact. We know that immigrants go to big cities, but that's where assimilation is strongest. We can't expect immigrants who undergo francization as a result of contact with other francophones to be any more resistant to assimilation than old-stock francophones. So the danger of a perverse reaction remains.
I'd like to talk again about the importance of properly integrating immigrants. For example, if we allowed more immigrants to settle in locations where the French language is already relatively strong, they would help to preserve French. I'm not saying they shouldn't settle in the big cities, but it would require complex gymnastics.