It is a very good bet that Canon has known for quite a while what the competition is coming out with, and an equally good bet that they are at least 4 years into the developement of their mirrorless FF camera. I rather doubt that they are jiggling time lines because of the competition..... if their camera is better, they want it out now to dissuade people from going elsewhere, if it is worse, the want it out now because of the embarrassment of releasing an inferior camera after the competition releases a better one.
Odds are, they are either finalizing the software and getting the last bugs out before the big announcement, at which point production starts, or production has already started and the announcement is imminent