Whether Canada remains a member of the Commonwealth of Nations or not is a completely separate issue to that of changing to a republican system. Many Commonwealth members, while keeping ties with Britain and other former British colonies, are republics with their own heads ofstate. Just as India was able to change to a Parliamentary Republic and remain a prominent member of the Commonwealth, Canada's adoption of a republican system will not have any affect on Canada's membership in the Commonwealth. For more information on the Commonwealth of Nations, clickhere.