The theme of the gathering is extended in this verse. However, the contextual gathering for Isaiah would typically be that of Israel, for it is historical Israel (as the term for the Northern kingdom) that is dispersed in the Assyrian conquest. However, this verse specifically gathers Judah from the four corners of the earth. This is the first indication that Isaiah's vision extends to the further future, to the time of the Babylonian conquest of Jerusalem. It is only at that time (the time of Lehi's exodus from Jerusalem) that Judah itself is scattered. Yet one cannot gather together from the four corners that which has not been dispersed to the four corners. Clearly Isaiah refers to the final gathering, made essential because he has seen the ultimate dispersion of Judah, coming a hundred years from the time of the prophecy.
Because one of the scholarly arguments for the dual authorship of Isaiah stems from the putative "deutero-Isaiah's" concentration on the events of the Babylonian conquest, the presence of such clear foreknowledge in this early section would indicate that there was a prophetic understanding of that time, and therefore the idea that it could only be understood in a later historical context is undermined.