Will they be able to quickly? I thought one of the major problems with this and why they'd shied away from changing it in the past was that thanks to the UK's lovely convoluted constitutional set-up that all the Commonwealth nations would have to agree to individually pass the same legislation at the same time?
Yes, my understanding is that the thrones of Canada, Australia, the UK, etc are all very separate, and the only reason we share a monarch is because we started with the same people, and have the same succession laws. If there was a theoretical case where, say, Prince William, as king, had two children, an elder daughter and a younger son, and the UK changed to absolute primogeniture but Canada didn't, you'd have a Queen in the UK and a King in Canada, and from then on the royal lines would be split.
Which, incidentally, as a Canadian Monarchist, I don't think would be a terrible idea. I'm constantly worried that some decades in the future we will become a republic. I think that if we had a Monarch that resided in Canada, there would be more support, reducing the likelihood that we would ever become a republic, my worst nightmare.