As for Calgary's size....
"It's land mass covers over 5,000 square kilometers making it the single largest metropolitan city in North America."
And as stated...we have no natural borders, no limits to land....
But we certainly do not have the infrastructure and roads to cope with a higher population.... nor are they seemingly possible to build..... Calgary has to be the worst "designed" City I have seen. Probably casue no on expected us to end up this much bigger then Edmonton.