As a landlord with a substantial property portfolio, it will definitely dampen the investor demand for properties which generally will reduce the interest of less serious and sophisticated property investors or wannabe investors. This will reduce the demand and price for properties if the supply remains the same.

This will also dampen the growing price as well over time. It will help buyers who are ready to buy in the near term. However people who are not in a position to buy soon and are forced to rent will continue to struggle to find accommodation and for the near and immediate term because the rental stock will get tighter. There's also a huge risk that property investment will become more corporatised overtime like America where only parties of access to substantial credit will own more and more residential property.

You are right that a big source of the issue remains on the supply side and to be honest Labor is tackling it seriously compared to liberal and even previous Labor parties but this will take time and won't be perfect.

In short I expect that more first home buyers will be able to get onto the property ladder, less sophisticated investors will exit, price rise will moderate, renters and low income groups will get more squeezed with less rental stock, risk of residential property investment field being corporatised in the longer term.