What hope do our children have to buy a home in Australia in 20 years?

No. In 1980 it cost around $25,000 -$45,000 to buy a very modest home in suburban Melbourne. The exact same questions were asked back then. Petrol was around .18c a litre and we screamed blue murder when it hit .23c. Average wages was around $98 per week depending on your job. Wages today are around $1000 pw and a modest home in the suburbs costs around $400k. It's about the same, just more zeros. In the 80's you needed around 30% deposit before the banks would talk to you, today you can buy a home with just 10% deposit. If your goal is to buy a home, you can/will make it happen. If you believe it's too hard, then it will be. There are so many things our younger people can do to save money and get themselves into a home, and yet I see so many young people not willing to do what they need to do to achieve this.
It wont happen overnight, you need to have a plan.
Our kids today have so many options available to them to help buy a home, something that baby boomers didn't have.
I don't believe they will be a generation of renters, more options will present themselves as time goes on and those wanting to be property owners will be.
Time will tell.