You're making a bit of an oversimplified point there. The reason the Expos eventually died was because ownership lied to the fans about getting a new stadium. I vividly remember Jeffrey Loria buying some land and even mock ups of a new stadium on the drawing board. The team's previous ownership was cash strapped near the end as well. They played in a crummy stadium and were selling off their best players almost every year.
Not exactly a recipe for a solid franchise.
Toronto would be a different story as ownership would have more money then they know what to do with and Rogers Centre would only be a temporary home as there would definitely be a new stadium built.