Were full cost accounting of the full economic effects of larger capacity pipelines to be evaluated comprehensively then they may be stopped by governments themselves. Conference board of Canada is predicting primary vehicle purchase will be electric cars in 8yrs http://www.conferenceboard.ca/hcp/hot-topics/environment.aspx. 

Every day renewables become cheaper and more efficient. Gains will be seen in the way these technologies work in Canada's tundra. 

Citizens see the impacts on the economy and environment long term while politicians look to the next e-day: BC doesn't need a pipeline they have tourism worth billions that a spill would imperil. The resistance to more oilsands development rests in the lack of reclamation and the cost of remediation on abandoned sites after corporations pull out or dissolve. You can watch this in Alberta today with the orphan well debacle.
When will Canadians see the diminishing returns of further large scale fossil fuel extraction?