No, it isn’t the sales or reviews of LA Noire, which aren’t bad but aren’t great either.
The reason that Team Bondi are extremely unlikely to release another AAA title is that back in 2004 (when the studio’s first title was estimated to be about 3 years from release) the Australian $ to United States $ exchange rate was about 0.7885 i.e. every $US was worth AU$1.27 (according to the Reserve Bank of Australia’s historical data).
Today every US$ is worth AU$0.93, with no decrease in the price of labour, rent or other employment factors (and there are plenty of employers who would argue that the cost of everything has gone up since 2011). That’s a 37% weakening in the US dollar compared to the Australian dollar over LA Noire’s lifetime.
It just isn’t cost effective to develop a large game in Australia when it would be cheaper to do it in the US (and much cheaper to do elsewhere). Unless Team Bondi could find a way to massively cut costs – such as laying staff off, relocating all or part of the studio to a cheaper country or reusing the developed art / material for another title or sequel – it would be unlikey to be able to get another AAA title out the door because it is just too expensive.