Canada’s emergence as a major gas-exporting nation is looking less like a pipe dream, with the announcement Wednesday of a third major pipeline to carry B.C. gas to proposed liquefying plants on its northern Pacific coast for exports to Asian markets. But with supermajors such as Royal Dutch Shell , Chevron and Malaysian-owned giant Petronas investing to develop the gas sector here, Ottawa needs to take more of a leadership role to ensure Canada lives up to the vast potential before it.