Usually a league commissioner will won't say anything to get peoples hopes up. I would interpret that statement as a strong endorsement for a team in Montreal - as long as a new baseball specific stadium is built. If a stadium does somehow get built, it most certainly has to be downtown. For baseball to survive, you need a great ball-park experience. Retro style stadium with a spectacular view of the city or water, and situated downtown, preferably in the historic district. Not sure if Montreal can meet those criteria.
Makes me think though, Vancouver could meet those criteria. There's a large area where the Whitecaps owner was proposing a soccer stadium right on the waterfront, with a spectacular view of the mountains, and it's just off of Gastown. Build a top notch AAA park that's expandable to MLB standards and you've got a realistic path to major league baseball. If the commissioner is willing to consider Montreal, why not Vancouver?