I'm of the exact two minds that you predict. I think Annual Passes are in quite a demand for the little park. I can't say i'd buy one, but there'd be plenty of Sunny Coast residents who would...
But as you say - would that then kill the 'no queue' charm it has?
If they're going to expand in these leaps and bounds, they may get away with it - more attractions means they can handle more people... the trick is that they need to set the pass at the right price point - too high and people will call them a rip off, too low and every tom, dick and VIP passholder will be in like flynn.
The problem is the big parks have conditioned everyone to a $99 price point. I think AW needs a higher point, and in my opinion, they'd probably justify $150, but i think they really need it to be closer to $200-250 for it to have the right effect (or maybe like $700 for a family of 4)... the problem is - would people pay it?