I think GM has made its intentions very clear in recent times. Car production in the US is being cut back with numerous models being curtailed, car plants being closed and truck production being stepped up. Sedan production seems to be transferred to China. The sell-off of Opel, dumping of SAAB and closure of Holden emphasises the company's plans. I reckon the Australian car production suffered because of the weird support of the US market for buying trucks as daily drivers. They are the most profitable vehicles to build and enjoy a huge proportion of an enormous market. For the world demand for GM cars, rather than trucks, China and Mexico provide cheap labour and plants like those in Korea and Thailand take care of other market sectors such as small and mid sized SUVs and medium sized 4 door utes.
Australia was never going to figure in long range plans due to our far higher labour and power costs and corporate tax rates. I believe the decision to shut down Holden really started with the GFC, not five years later in 2013. Once it became necessary for a government bail-out, GM started to look seriously at cutting models, rationalising and selling off plants and brands and abandoning traditional markets to survive. They haven't finished yet. I reckon we all know who's next.