Overall, the scene foreshadows Winston's development as a rebel against the Party. Given what we already know about the Party at that point, it seems unlikely that this will end well for him. It is difficult to say that the sequence involving his mother and young sister foreshadows much in the story, indeed it seems more intended to provide a window on what things were like before the Party took over, and, given that it is mentioned that his parents likely disappeared in the purges, it gives hints as to how the Party actually rose to power. Clearly, the scene involving the young woman foreshadows his affair with Julia. On the one hand, he says her flinging off her clothes is a gesture that belongs to the "ancient times," on the other, it presages his rendezvous with Julia in the countryside:
The girl with dark hair was coming towards them across the field. With what seemed a single movement she tore off her clothes and flung them disdainfully aside...What overwhelmed him in that instant was admiration for the gesture with which she had thrown her clothes aside. With its grace and carelessness it seemed to annihilate a whole culture, a whole system of thought, as though Big Brother and the Party and the Thought Police could all be swept into nothingness by a single splendid movement of the arm.