I was never counting anyone out in my list. I was making a guess.
Calgary does have some nice lots for a super-tall. It's difficult to say what the next oil company will do when they build new, but it's going to take a few years to build up demand for office space again. I'm pretty sure Calgary will get a 300m building within twenty years. It did take a good quarter century to top Petro-Can (Suncor) as the tallest. I threw Hamilton in because they actually had a somewhat ludicrous proposal in the Connaught Tower and it seemed like most people were forgetting that fact. While Niagara Falls has had a few 200+m proposals go the wayside they do have a 170+ building right now and I believe entertainment/gambling has a better chance at building super-tall height than commerce at this point in time. Of course, I could be wrong and the 310m MoneyMart Centre could be built any day now.
It's going to be a very close race between the top three or four cities for which one gets the hole dug first. I also believe it's going to be a while before we see it. I'd say 10 to 15 years before there's a piling going in.
I agree with Architype, although I would be a little more generous to Canada and say 225m is a super-tall.
I'm curious as to when people think the front-runners will build a new tallest for the city let alone the country.