The poll certainly leaves the next election wide open but we need to consider three separate things that are going on.
(1) Midterm shrinkage of minor parties. The smaller parties have consistently polled poorly in midterm but increased their support in the election campaign when they get more exposure. The combined vote for parties other than Labour or National was 38% (33% for the parties in parliament at present) at the general election compared to 18% in the latest poll. They may well get most of this back at the next election.
(2) An overall left-right swing. The combined Labour-Green-Progressive-Alliance-Maori
vote has gone down from 51% at the general election to 47%. The combined National-Act vote has gone up from 28% to 46%. This corresponds to about a 10% swing.
(3) National has drawn voters from ACT, NZ First and United. Although it's difficult to differentiate this from the combined effects of 1 and 2.
If the two major "blocs" come up about even but support for the minor parties (in particular NZF and UF) returns to about 2002 levels then the ability of the major parties to compromise will become critical.
We live in interesting times.