Concert venue in quotes because:
a)Toronto doesn't need another stadium venue for large concerts. It has Rogers Centre in the downtown core which is a much better location. There is limited transit access to Downsview but a lot of space to build parking lots. (You know, places where people park and tailgate for a certain sport that occurs on Sundays)
b) Only a few artists per year who can sell out 50k plus seat stadiums visit Toronto each year. This venue would give them more flexibility for summer dates as Rogers Centre is often booked for baseball but seems to be a fairly limited market. I think Rogers Centre is hosting maybe 10 non baseball events a year. Hardly seems like a good reason to build a new stadium. (Unless you had a guaranteed tenant that played at least 8 home games a year- on top of the summer concerts you could put on when Rogers Centre is busy for baseball)
c) The stadium already has naming rights. "Rogers Stadium". (Hmmm, is that the same Rogers that just bought a majority stake in Maple Leafs Sports and Entertainment, that already owns the Blue Jays, and has said they would be interested in bringing an NFL team to Canada.)
So, Live Nation will build a 50k seat "concert" venue in Toronto and when the time comes Rogers will propose to expand it to 65k seats or more and use it as an NFL stadium. In the meantime Taylor swift can sell out 5 shows a year there.