There's been a broad agreement across all parties to not change the EV incentives until there are 50k zero emission vehicles on the road or 2017 arrives. We'll reach 50k zero emission vehicles this month or possibly next month.
As a result, the sitting parties have launched an extensive review of the EV incentives and in fact the entire current car tax system. They will be looking at what works, what doesn't, and come up with a policy for the next few years. This is a process that is ongoing as we speak, and the results are scheduled to be announced in May. And then, changes to the current system will probably not come into effect until 1. january 2016.
Now, what they will actually conclude is anyones guess. You have four parties who will all want to have their say:
The Progress Party - Basically christian conservatives with a strong populist streak. They are against taxes, and pro-individual freedom. They've for instance legalized the Segway. I would say they are conflicted by loving that there are no taxes on EVs, but hating that the lower taxes for EVs cause other cars to be taxed harder. Also, they don't believe in anthropocentric climate change, though they do concede that NOX, SOX and particulate emissions should be avoided.
The Conservative Party - Old-school conservatives (though not extreme). In my opinion they are trying to be viewed as a responsible adult that you can trust. They want to save the environment, and their Environment and Climate minister has promised a 40% cut in carbon emissions by 2030. They also want to be fiscally responsible.
The Christian Democratic Party - Basically feel-good christians. They are for helping refugees, old people, children, as well as saving the environment and the world.
the Liberal Party - Basically pro-(small) business and pro-environment. They are the most vocal supporter of the EV incentives.
The way the dynamic works, is that the Progress Party and the Conservative Party are in a minority government, and are completely dependant on the support of the Christian Democratic Party and the Liberal Party. The support of just one of these parties is sufficient to get policy through the parliament, but there is an agreement of cooperation between the four parties, and the Christian Democratic Party and the Liberal Party have worked together in standing up to the minority government.
How this works in relation to the EV incentive review: The Progress Party and the Conservative Party will be trying to cut down on their least favourite incentives (access to bus lanes is probably first on the chopping block) and they will probably also try to cut taxes. The Progress Party will also be trying to make the car tax system as favourable to the cars their core voters buy (mostly reasonably priced family cars). On the other hand you will have the Liberal Party, hopefully with the support of the Christian Democratic Party, trying to keep as much of the incentives for as long as possible.
Personally, I think the most important incentives (exemption from 25% VAT and exemption from additional car taxes) will last a few more years, with a gradual phase-out over a few years. Maybe in 2020 the incentives will be gone.