The key issue is as Michael Gleeson explains the AFL and Rugby League working around the World Cup schedule to free up the stadiums. The question is why would they. Soccer poses a serious and credible threat to their popularity.
Its been a climb since Johnny Warren wrote his memoir documenting the biases of the rabid fan base of Aussie rules. Some of it still persists but Australia is not the isolated outpost of yore. The hinterland might occasionally simmer but there is no escaping a thriving country very much part of the global economy, a huge driver of quality education, with a relatively transparent immigration process that attracts thousands.
From a soccer standpoint, Australia is now part of the Asia zone where millions follow soccer. It is a much tougher group of countries to play against. Most of the nancy boy derision that soccer faced was because of the weak competition in the Oceanic zone where they would run up scores against Western Samoa. Politically too, there is a change. John Howard's us and them fear mongering was fiercely rejected by a majority. The new PM, Kevin Rudd has ushered in a new era of reconciliation with a long due apology for the inequities suffered by the indigenous people of Australia. A mere band aid with much more to do. But it is a start. Soccer is part of Australia's re-evaluation of the past and its ability to move forward.
For what it is worth, Aussies are sports lovers. If a sport has a chance to flourish, introduce it in Australia first. There is nothing that they do not play and they become incredibly good at it. Every sport has a well supported niche and soccer has after a rough start, established itself. There is also no drop off in rugby's popularity in countries that also play soccer. Both sports enjoy separate audiences.
In the end, the AFL and Rugby League stand to look pretty small minded and insecure if they do not work with the World Cup bid committee to sort out this scheduling issue. Their fears are unfounded.