No, it's silly to assume that people would let society collapse under socialism. In your house, do you not clean your toilet because you don't have an incentive? Do you not clean because you don't have an incentive? Do you let your house fall appart around you because you don't have an incentive to fix it?
In a world where our choices do matter and where we can decide things collectively, once we get rid of the State and bosses and do direct democracy in the cities and in our workplaces, we will necesarily feel responsible for the well being of the whole. People will naturally do the minimum work required to reach the standard of living they want.
Just think about it: if the people are in control and get the entire fruit of their collective labor, if they feel too poor, they'll just work harder to be less poor. If they feel like they work too hard, they'll figure out ways to work less without making sacrifices. We just have to stop thinking that our decisions and actions don't matter and can't change a thing, like we've always been taught!