The point of this story is that the majority of the people in Omelas do not struggle for survival at all. They willingly exchange the intense and terrible suffering of one little child for their own happiness. This is the exchange that allows Omelas to be such a great, wealthy and contented city.
It is only the minority who respond to the scene of this young child and her suffering who are unwilling to enter into this somewhat Faustian bargain. They are unable to settle for their own happiness and the happiness of their city being built upon such profound suffering. They leave Omelas and enter a completely unknown and uncertain future:
They leave Omelas, they walk ahead into the darkness, and they do not come back. The place they go towards is a place even less imaginable to most of us than the city of happiness. I cannot describe it at all. It is possible that it does not exist.
The struggle for those who leave Omelas is shown in the complete uncertainty of the narrator regarding their future. They leave security, wealth and happiness and exchange those for a complete unknown. Their struggle to survive is not commented upon apart from the reference to the "darkness" that they glady enter. Although they face an uncertain future, the narrator indicates it will be a happier one, in spite of the struggle that it will entail, because they will be free from Omelas and the exchange that it is based on.