Considering that Turner Field is used a minimum of 81 times a year for baseball alone and will be redeveloped after it's closed, it's the complete opposite of a white elephant. It has been very well used over the last 20 years and is a model of what's possible for an Olympic stadium. The Atlanta Braves moving has nothing whatsoever to do with the Olympics or the concept of downsizing an Olympic stadium after the Games. It has more to do with the stadium's location and the fact that sports teams in the US routinely find fickle reasons to move out of their stadiums for something shiny and new. Their other excuse is that the stadium needs work, but so does every stadium after 20 years.
A large part of the cost of every Olympics is paid for by the private sector. In Atlanta's case, the private sector paid for the venues, including the Olympic stadium. And those Olympics made a profit. So no, Atlanta's baseball team wasn't subsidized to the tune of hundreds of millions of dollars. A deal structured the same way in Toronto could see an Olympic stadium with temporary seats to later become home of the Blue Jays, Argos, and/or TFC, and paid for by Bell/Rogers/MLSE and any number of sponsors.