It is increasingly a problem. We have heard about it in British Columbia, where French-language school systems were accepting virtually anybody.
I also know that, in Manitoba, more than half of students starting kindergarten in the Division scolaire franco-manitobaine do not speak French. They are then francized. This is a serious problem that reflects the changing nature of the francophonie in minority communities.
The French-language school system in Ontario is managed by francophones. They accept everyone because they understand the necessity of doing so. That can clearly have an impact on the schools offering immersion. However, if you think about it, it helps francize many students. That may be one way of operating.
Promoting bilingualism will clearly attract more young anglophones wishing to learn French, and that has value.