The picture is certainly being painted as optimistic. However the decisions to build those towers currently under construction were made 1-2 years ago. There is hardly a shortage of supply now. All of the new rental buildings that opened in the couple of years ...., SoDa, Underwood, Portfolio, The Hat 7th Ave & East Village, Aura 1 & 2, The Metropolitan ..... all have units available. I am not so sure the same market conditions exist today particularly with the uncertainty of the pandemic.
Who really knows what will happen as the uncertainty is off the charts with COVID impacts and we are in truly wild economic times - but all data points to Calgary's population continuing to grow, with new household formation (i.e. a single or couple that resides in their own place) trending slightly higher than population growth. This is true for all Canadian cities, Calgary despite all the doom and gloom, remains in the faster growing cohort based on the most recent data available (spring 2020).
Canada as a whole - and Calgary a bit behind - has for decades trended towards smaller family sizes and increases in single-person households - exactly the markets supported by apartment living. As Calgary continues it's trend towards the Canadian average (less wealth, less growth, more stable), I would expect us to play catch up and see continued growth in that market. Combined with generational factors (either from less ownership preference or less ability to own due to economic realities of next generation of young adults) I don't see why construction won't continue as normal with the predictable short-run overbuilding, pause, market tightens, building cycle.
I mentioned this before, but Calgary would require some ~60,000 purpose-built rentals to hit the Canadian average for purpose built rentals as a portion of the housing stock of the 10 largest CMAs. And we are talking just the average - every city bigger than us is well above average in rentals. Structural, historic and regional differences will likely prevent us from ever reaching too close to our larger counterparts or the national average, however if only half the gap was closed (30,000 units), and half of purpose built rentals were built inner city, that's 15,000 units - so another whole Beltline worth.
In a supply and demand argument, I would more worried if I own a generic 1970 - 2010 house - Calgary has hundreds of thousands of these. Demographics and economic pressures are shifting away from this housing type, as it's the most expensive housing type to live in under pretty much any market conditions. They will always be someone to live in them of course, I'm predicting below long-run average growth in these household types.