There is certainly some isolationist rhetoric coming from some quarters of Congress so the likelihood of the law being overturned are very slim. Also, the USAF has unsuccessfully lobbied to get more than 180 F-22s so I don't see the RAAF being an exception.
US industry aren't in much of a hurry to lobby overturning the law since LM also produces the F-35. Australian industry also would prefer the F-35.
I see the request as more of an attempt to differentiate themselves from the previous government but the end result will be the same.