I think immigrants make a huge impact. Want an example? watch 'Masterchef" and you will see the contestants making pasta one night, and a stir-fry the next. Go to the city and you will see italian, chinese, indian and mexican restaurants on the same street. This does not change after a generation. European migrants have already been in Australia for a generation already, and foods like pasta, curries, noodles and hot-dogs are eaten by many people, not just those who eat it as part of their culture. I'm using food as an example, but migrants changed Australia a lot. Migrants even shaped Australia into the way it is today. Remember that, with the exception of Aborigines, all families in Australia were migrants at one point. Don't bother trying to tell me that the Aborigines played cricket. People in Australia even celebrate some cultural festivities and celebrations, even if they have absolutely nothing to do with the culture in question. I have seen people of many races celebrate the Chinese new year, as well as plenty of buskers with kilt, bagpipes and all, who aren't Scottish. Add to that Irish dancers who aren't Irish, Asian and Indian Christians, I think you get the idea...

I may have been biased in my comments about sport in my main argument, but there have been Australian customs are have been diminished as new waves of migrants come in, like being patriotic and love of meat pies.