The devil is in the detail, and as far as I can tell there is no legislation on the table, only a statement of intent. Your only safe source would be advice from government, but historically if they give you bad information they will take no responsibility anyway and you could cop it. I suggest your best avenue would be to lodge the question with your local state member, as well as Treasurer Tim Pallas. Considering the lightening speed they answer honest questions you may be best served by watching and waiting.
My cynical nature expects that while stamp duty might go down the cost of properties will rise by the same amount at the same time, or close enough.