Air New Zealand, for instance, pretty much needs ETOPS 330 to make the most of its 10 787-900s now on order.
No it doesn't. The 773 has greater than 180 min EDTO and yet hardly ever uses it. The Pacific can be covered using 180 min quite effectively to get to the US going one way or Asia going the other. South America, if it ever happens, can be made using 180 min.
The extra range of the 789 would not be operated under EDTO rules, i.e. the first part of the flight will be EDTO due to location in the Pacific. However a long range flight to either the US or Asia would most likely have an EDTO exit point long before the end of the flight.