There does not appear to be any concrete evidence that ending negative gearing will reduce property prices, in fact, most of the evidence has heuristics biases.
If negative gearing ends the number of properties available for tenants to occupy will decrease. This will push rents up. When rents increase this attracts other types of property investors into the property market, who are interested in higher yielding investments which will, in turn, put pressure on property prices to rise. All that happens, is you replace one property investor with another type of property investor and the rents go up!
Most of the current investors who use negative gearing are middle-income earners. By ending negative gearing and replacing it with yield-driven investors you will make the rich, richer and the poor, poorer!
It is unlikely that either political party will lower the immigration intake to try to slow down property price growth.
The final elephant in the room which is unspoken about is the huge amount of property that has been purchased by overseas buyers. There is a number, who are able to bend the FIRB rules. Think of this, if the Australian dollar is low and you expect it to rise in the medium term, as an overseas buyer you have dollar capital growth, along with property price growth, they win two ways. The Sydney property market is a safe bet for most overseas property buyers, unfortunately, this pushes the locals out of the Real Estate property market.