The new Chief of Defense staff isn't keen on women in combat roles, I believe. I don't know if he feels that way about all combat roles, or only some.
That being said, there aren't huge numbers, especially if you don't include the air force, where arguably the situation is different.
One of the arguments against it is that in a lot of combat scenarios, especially for the army or Marines, you are essentially saying there will be mixed sex accommodations, toilets, etc. With potentially little or no possibility of privacy.
There are also questions around things like access to contraceptive medications, and a lot of women in active combat roles use these to suppress menstruation. Menstruation itself can be a problem where there is no privacy or where it affects performance.