I can't see them stopping the service to/from MEL. I've been on it a lot, and whereas the loads aren't as high as the SYD-SFO or SYD-LAX flights, UA gets a lot of business from MEL with the MEL-SYD flight.

When I saw the topic, I thought the OP was referring to the MEL-LAX seasonal flight. It ran last year from approx. Dec - Feb. I haven't seen anything about it for the coming Dec-Feb season. Doesn't look like its happening.