One of the questions that comes up on this forum persistently is whether NZ will start or exit long haul routes.
Historically as we all know airlines persisted with loss-making long-haul routes for years and decades because aviation was a somewhat government-directed and owned business. And although Air New Zealand is now largely government owned again its persistence on loss-making long-haul routes is not totally crazy. Airlines after all amortize the cost of aircraft over a decade or more, so taking a long view on other costs is sensible.
One presumes that with a lot of long-haul routes there are also long-term contracts with employees and the like that would be costly to exit (and perhaps even to reduce below a certain frequency). So the airline's decision on persisting with London or whatever other routes are in question is presumably that total exit now followed by re-entry in 201x would be far, far worse than persisting through some losses now and hoping that the world economy recovers.
Are they losing money on Shanghai? I would guess so. But it's not crazy to think that over 10 or 20 years a large country with whom New Zealand got an early free trade agreement will generate profitable air connections (even accounting for those years of early losses).
The more problematic market to me seems to be Japan, where the historic demand for tourism seems to be weakening, and the volume of trade between the two countries seems to generate less air traffic than with other trading partners.