ViewFromTheWing provides analysis on this "development". United operates 462 flights per month between the US and Australia versus Qantas' meagre 316.
If we count alliances, between the US and Australia, Star Alliance is still on top with 462 for United versus 378 for OneWorld (AA and QF).
I don't think United will drop from 462 flights per month to Australia down to 42. If you are referring to on a weekly basis how many flights United operates, I doubt it'll doubt to 42 either since that would mean going from 462 flights per month down to 168 which would represent a huge drop.
I could totally see Alaskan replacing the A330s with 737s to keep the fleet harmonized. Just offer a Hawaiian hopper service to SYD and TYO.
Technically Bombardier C Series which again is something Boeing is lacking (small jets). Perhaps they can replace it with Dash-8 puddle jumpers.