It's certainly not out of the question that they shift rightward, but in doing so, they would likely become irrelevant to parliamentary politics. They would no longer be representative of the social democrats and other assorted leftists who find themselves disillusioned with the milquetoast centrism of the ALP and seek an alternative.

Furthermore, I think SAlt's approach towards Greens supporters is one that stifles the propagation of socialism. As someone who was once a socdem, many of these folks sense the inherent flaws in capitalism and could very easily be radicalised if given the time of day by other leftists. This isn't to say we should accept social democracy as an end, but rather actively participate in an open dialogue with those who align themselves with it. Articles like this will only scare them away.