Australia primed to be yanked into US (
http://www.news.com.au/common/story_page/0,4057,6760977%255E421,00.html)
I wouldn't be surprised if this did happen in the next 50 years.
The reasoning is that Australia's relationship with the US is very closely tied. Basically, what we are seeing is that if the US goes to war, for Australia it is not a case of whether we will join but what forces we will send. This is how it was with Britain in the first half of the twentieth century when we became a federation. In the latter half we saw this with the US.
I really can't see how the US and Australia can forge too many more agreements without some sort of amalgamation of the two countries.
However, these agreements are not all known to the wide public. There are agreements dealing with Intelligence and R & D of technology. EG Pine Gap, which is US soil located on the Australian mainland. On the intelligence side, some agents who work for Australia actually answer to the CIA. A guy is in solitary confinement unable to speak to have contact with anyone because of divulging this information.
Personally, I'm not sure if this would be a good thing to do, but I can definitely still see it one day happening. So, I wonder if there is room on that flag for one more star, or will they tell us where to wipe it.
BTW if you read the article linked above, don't take the stuff written about Australia in a paragraph you will notice as true. Except for the Prime Minister not living in The Lodge (US equivelent of the White House).