A very interesting question you bring up here, NWstubble. This has been
marty998 raises some good points here. For the sake of this thought experiment, let us assume the change, as with any societal change that occurs on a larger scale, wouldn't happen overnight. Although some groups of people and industries would cling to the consumerist method of the 'past', the economy would adapt. The way I see it, there would be no collapse as this would be a gradual process that would be driven from the bottom of the pyramid, i.e. humans, and the layers above, notably the markets, the financial sector, businesses, would need to adapt or they would lose lots of ground.
I agree that our current economy and financial sector is based on consumerism, but I believe that it is the people who have the power to dictate what kind of change they want to businesses, and not the other way around.