"And if the pro-growth argument wins the day, then what? Inching up to a 10 million population mega-city? 12 million? More?"

The is no compelling reason why Sydney or any other Australian city needs to dramatically increase the size of its populations. If the aim is to maintain a good living standard for every resident, then smaller tends to be better.

Sadly, vested interests have captured our political establishment and have forced the current population deluge upon us. Immigration has been ramped up at the behest of the growth lobby. The interests and wishes of ordinary residents have been totally ignored when it comes to population policy.

To quote economist Leith van Onselen:

"This is a disaster in the making. At this [current] pace of growth, Australia will add one million people in just 2.5 years, with the lion’s share flooding into Sydney and Melbourne.

As a result, living standards are being unambiguously smashed. Housing is becoming smaller and is hideously expensive. Roads, public transport, schools and hospitals are crush-loaded. And overall economic and social infrastructure is groaning under the strain."

http://www.macrobusiness.com.au/2019/06/population-growth-surges-past-400000-rising-immigration/

No amount of 'better planning' will fix this population crush.

The recent Infrastructure Australia Audit found that the costs of overcrowding and congestion will double by 2031 to reach close to $40 billion under the current business-as-usual approach. See: http://www.thecourier.com.au/story/6331590/we-must-ignore-the-doctors-orders-and-treat-population-growth-properly/

Meanwhile, the 'Big Australia' mafia has basically told long-term Sydneysiders that they must sacrifice their living standards for more migrants. Link: http://www.macrobusiness.com.au/2019/09/sydneysiders-told-to-sacrifice-living-standards-for-migrants/

We're on a road to misery.