Are they going to be making adjustments in the code for investment in businesses? Because, typically, the reason you invest in property and similar investment vehicles is to avoid risk while achieving steady, if limited, growth. Businesses are typically a high risk investment. Even large businesses have historically been seen as risky propositions in comparison to property investments, and rightly so.
Moreover, if you make investment in housing more expensive for the holder of that investment, why on earth would you presume that the consequence would be cheaper housing? The most likely result of such a tax would be the aggregation of such properties into the hands of those who can operate such in volume in order to maintain profits, as those who can no longer make a living off of small property units sell to those whose living is made off of groups of property units.
When government acts to increase unit costs, the result is operation/sale of larger aggregations of units by fewer operators in order to maintain profit via multiplying the small margin per unit.
Our government has generally been fairly low in the interference stakes for about 20 years. "We have leveled the playing field of international trade, but we're the only team playing without a box" was a quote from the mid eighties. Our problem negotiating free trade deals is that we have nearly no tariffs or import restrictions so we have nothing to negotiate with.
I'm pretty sure the current (right wing) government removed the incentives for R&D because they didn't see it as important.
The reasoning behind the capital gains tax, as I understand it, is that there are a bunch of people making isk off investments in property who don't pay any tax on that income. (this also applies to people making money by investing in
ponzi schemes shares who get no dividends (which they would pay tax on) but make money by having the price go up because more people are investing in it.) and that this means that if investors have a choice between investing in productive capital (which returns a dividend) and investing in unproductive residential housing, they're choosing the housing.
Combined with the memories of the 1987 sharemarket crash which saw a lot of people take a bath on their share investments, this has made it very difficult for NZ business to raise investment funds inside NZ, since nobody wants to move away from safe as houses property. That has a side-effect of meaning that they do a lot of sourcing of their investment money from overseas, so most successful businesses get bought out and all the profits head overseas...
Various right wing people (including the head of the NZX stock market) are trying to get the government to sell more of it's profitable monopolies to try to get more shares on the stockmarket that are worth having, since a lot of the existing shares are crap at the moment (highly paid executives do not seem to be able to make businesses that are worth investing in in NZ, at least compared to property currently)
A side effect of everyone wanting to invest in property is that there is more money chasing the same number of houses, which drives the price up. This not only puts houses out of reach of people entering the market, but means that tax-free capital gains encourages more people to invest their spare money in the property market. This combines with a lot of city council rules about trying to keep green belts that limit the available properties for new building, which also drives the prices up (more capital gains!).
If there's a captial gains tax, then buying a house and waiting for it to get more expensive is not going to make you as much money as putting it in the bank or buying govt bonds. Which means fewer people will bother buying a second house as a rental, which means less money chasing the same number of houses, which means it gets harder to sell them, and the price comes down. That's the theory anyway.
A lot of quite respectable economists from both the left and the right have agreed that a CGT would remove a particularly distorting affect on our countries economy. It's also a way of pissing off all the upper middle class people who's idea of investment is to buy a second house, rent it out to cover the mortgage, and wait for it to double in price, which is why politicians are often reluctant to consider it.