Francophone immigrants do stay in Ontario. I would even say that a number of francophone immigrants from Quebec come over to Ontario. Ontario attracts immigrants, whatever their language. Our difficult is in recruiting francophones in sufficient numbers and I am not sure what kind of problem we have: is it a retention problem or a recruitment problem? I confess that I am not an expert so I cannot give you any statistics on it. I believe that the situation in Quebec is different from the one in Ontario. Quebec is losing not just immigrants who speak English, but also those who speak French. It seems to me that the statistics indicated that, the last times I consulted them.
On April 30th, 2019. See this statement in context.