The reality is that Keating un-quarantined NG, though, presumably because of political pressure. It almost doesn't matter whether axing NG will cause rents to rise and prices to fall (I think it will, but that's just me). I say almost because there is a slim chance voters might see the big picture instead of focusing on their own situations, but I doubt it. I remember some article that said that people want more affordable housing but not lower prices, because most of them own homes.
The opposition will mount a scare campaign making it impossible for any govt to do it. The key is not the investors: it's the renters (30-odd%) and the home owners (everybody else). It won't be hard for the opposition to convince voters that rents will go up and prices will go down.
There will be a lot of great ideas in the Henry Review that will make the tax system fairer. But there are so many entrenched interests and the opposition willing to sacrifice the truth to get votes that they'll likely be buried.