It's hard to predict something so far off, but I feel those numbers are realistic. If you had asked me 20 years ago, I would have predicted Calgary and Edmonton to be about the same population, or Edmonton having a higher population due to a predicted decline in the oil and gas industry. Things are different now though.
1) The decline in oil will be a slower more drawn out process, and much of that decline has already happened and Calgary was affected, but not to the extend many thought would happen.
2) Gas will still carry on for a while, and although it too will decline it's decline will be slower than Oil's decline.
3) 20 years ago the provincial government and even the federal government were generating far more jobs in Edmonton than Calgary, but this isn't the case anymore. Still more provincial jobs in Edmonton, the the gap has narrowed as jobs are now being spread out more around the province. Same for Federal jobs.
4) Over the past 20 years Calgary created a whole new industry for itself, in distribution, warehousing, transportation and aviation and has taken over as the dominant hub for the prairies and also can be argued for the whole of western Canada.
5) In recent years Calgary has become the 4th largest recipient of Venture Capital money for Canadian metros, and about 90% of Alberta's VC money goes to Calgary. I don't see a lot of change in that area anytime soon.
6) Some other intangibles like a much better connected airport, and proximity to the Rockies also help more than people think.
I don't want this to come across as an Calgary boosterism post, but these are things that are factoring into Calgary's growth.
