Personally, I think there is room for B767-300ER's in the fleet, at least in the short term. The 763's can fly the domestic routes and occasional international (NAN, DPS etc.). They would have about 230-240 seats. Mind you, the B767-300ER's are LEASED from AC, not bought. Sure, it might be capitally less intensive in the short-term, but if they were a part of a long-term fleet for AN, then they might have considered buying some.
The A330-200 would fill a niche of about 270 pax (since they would be operated in a 2 class config. If these birds were internationally configured, Asian expansion is likely. However, if the A330-200's came along, the B767-300ER will have to go unless AN can demonstrate that they can economically run two types in that range of the market.
Their current fleet of A320-200's is well-loved by the general public (at least the best-loved of a supposedly bad bunch) and is the last aircraft pictured on one of the 'Absolutely' ads. They're of about the same age as the B737-300's they currently have. I therefore think that it's impossible to tell which they're going to ditch. NZ still have B737-300's which may be the decider. It would be better economics to run NZ and AN B737's as a single unit I think. AN can buy some B737-700's or B737-800's as replacements.
The general public perception, who, let's face it, are the revenue generators for AN will, however, not see this and perceive the B737's as old, aging aircraft (even if AN bought 73G's or 738's). If they buy the A319, a type that isn't commonly seen (if at all) in Australia, then the public would PERCEIVE that AN had a newer fleet which would help immensely.
There's no point buying the A321, though the costs would not be much more. It would probably seat 165 or so and the size premium over the A320 (144) is not much and turnaround times at airports like SYD would be longer and may lead to slot problems.
I hope I'm not starting an A vs B war because I'm only pointing out perceptions of a very ignorant general public, of which I hope not to be a part of.
I could probably have written more, so if there's anything that should be added, please suggest, because time is limited at the moment.
M88, 722, 732, 733, 734, 73G, 73H, 742, 743, 744, 752, 762, 763, 772, 773, 77W, 320, 332, 333, 345, 388, DH8, SF3 - want