As a matter of fact, sir, you are referring to two different sets of data from the census. The first set has to do with Montreal Island and shows a decrease. The second set has to do with the metropolitan region, which is geographically larger, where there is a different picture that reflects what you just mentioned. Moreover, some francophones left the island and settled in the suburban ring around the island, either to the north or to the south, and there, the situation is slightly different. In fact, the census clearly reflects this state of affairs.
No further studies have been done. Statistics Canada published the census in December and we are not aware of any more advanced studies.