No European would seriously consider the reduction of population density that comes from admitting Canada to be a meaningful improvement to the EU. Canadian energy resources would definitely be welcome, but that's hardly enough of a reason to extend membership, especially since a trans-Atlantic power cable (which would be needed to get the most out of Canada's hydro) would be a beast of an engineering challenge itself.
Tighter EU-Canada integration is a much more important and achievable goal, as the article points out in the final paragraph.