According to http://en.wikipedia.org/wiki/Oath_of_Citizenship_(Canada) they have only changed the oath once, in 1977 when they added "Queen of Canada" after the name of the Queen.
I swear (or affirm) that I will be faithful and bear true allegiance to Her Majesty Queen Elizabeth the Second, Queen of Canada, Her Heirs and Successors, and that I will faithfully observe the laws of Canada and fulfil my duties as a Canadian citizen.