Depends on. Where do they colonise? The South East? It is pretty much isolated from, Indonesia let alone India. It could go eitherway. I'm inclined to say they may go Islamic IF Indonesian Kingdoms turn Islamic. But then again, Bali is an example of isolated Hindu region/state. So who knows.
P.S. I'm pretty sure Javanese etc knew about Australia. It is really too close not to know about it.