IMO, the best way to estimate the potential population that would come to Quebec City for hockey is using Quebec province regions. Start by sum the population of the following regions :
All this population live pretty much under 2h30 from Quebec city center and well served with new highways built in the last 10 years.
+ conservatively 33% of the following regions as they were pretty much splitted in allegiance when the Nords were there :
The majority of the population of these two regions live pretty much under 1h30 from Quebec city center and also well served with highways.
So this add up to a
1.6 million population. All the numbers are from 2016 census.
You can also add part of the regions that are in the far eastof the province, as Quebec city is the portal to Montreal anyway:
This is pretty much Nords classic population base ! Also, people needs to understand that Quebecers from regions love to do roadtrips. The Nords never had attendance issues even when they were the worst team in the league. I'm more concerned about corporative suites.