The problem I have with the aging population argument is that its lazy economics. We have a aged population who are by and large knowledgeable and active - a fair portion would want to work at least part time. The challenge is to integrate these people back into the workforce such as child care, care-takers etc. Similarly with young people we constantly hear there's a skill shortage; employers would rather import workers than train young people (not without some justification but you can't demand low taxes and then not train people).
Environment - that would be self evident I think. We are already past the population threshold IMO.
Culture - I would much prefer to live in a mono-culture. Not because I think mine is superior - when you're overseas its fairly evident who the Aussies are and they're not something to be proud of - but because the mono-culture that I know is safe. Like the Hungarians recently they have seen what's happened in Western Europe and they don't want to follow their example - what's wrong with that? We are lucky we found/stole Australia first. Lets continue the luck.
