To the surprise of no one, Air Canada announced today they are following Westjet's lead and are banning carryon baggage for basic fare tickets next year. Note: You still get one personal item.
https://globalnews.ca/news/10901245/...-fare-changes/
Obviously overhead bin space is at a premium, and this is one of their solutions. It would have been nice if they just enforced the rules over the years, but they didn't seem interested in doing that.