It would be nice, but I would bet it's a close call whether there's enough traffic to support it. NZ is a country of just 4M people. Not that many are coming here from NZ, and not that many people are going there for tourism. It's also not a huge regional financial hub either.
However, there's NZ feed from their AKL hub to Australia (including Perth) and the Pacific Islands. And plenty of UA feed on the SFO end.
NZ's product can be overrated (uneven staff, tight coach seating, lousy FF program, zero award space, aircraft maintenance issues leading to lengthy delays). So bring it on UA.