Alone among the writings of Isaiah, at least Isaiah son of Amos, is 32:12-14 in predicting the fall of Jerusalem. Apparently, according to the JSB, all of Isaiah’s writings save this passage describe Jerusalem being saved, though often just by a miraculous last-moment intervention by God. I guess it’s possible these verses were added later during the exile, but the editors of the JSB gave no indication that they suspected such.
JSB accounts 31:1 – 32:8 as a single poem; HarCol places a new heading at the top of ch.32. In JSB’s view, the poem moves from prophecies of destruction (31:1 – 31:3 or 4) through prophecies of salvation (31:4 or 5 – 31:9) and finally to prophecies of end times (32:1-8). I understand the tendency to call 32:1-8 eschatological, but I don’t take this view as a certainty: These verses might just refer to the time following God’s salvation of Jerusalem from the Assyrians. However, the remainder of ch. 32 has a similar move, with the final verses seeming more convincingly like end times prophecies.