It doesnt matter who these people are and where they're coming from, and why they're coming here.
The real question is, I dont know whether its been asked as Im not reading 7 pages, the real question is, can this country support a significant increase in the population?
We've already got major water and resource issues, and things arent looking any better for the farmers and growers, which impacts the local economies in regional areas, the capitals have turned to chaos due to the transport system, largly due to the heat wave.
Imagine if we had a 10%-20% spike in population in metro areas. Already the southern and eastern states are on high water restrictions, energy companies are talking about black outs, just this week, due to the increase in demand for power to cool homes. The fruit growing industry in Victoria is a shell of its former self, so theres less work for unskilled laborers looking for a life in regional Victoria.
To say Australia is a big place, is true. But a majority of the country isnt used for a reason. They're sitting around twiddling their thumbs right now trying to work out how they're going to fix our resource problems, yet at the same time they're wanted to bring more people in. Makes heaps of sense doesnt it??
Short answer. We're full.