It is a massive move historically to go from the coming judgment of Israel and Judah (and the accountability laid upon Assyria) to the establishment of a "rod from the stem of Jesse" (11:1), but theologically, this is simply the next movement. Only a remnant remains; only a stump. But from that stump comes forth One who has the Spirit of the Lord resting upon Him. Of course, every Gospel informs us of exactly Who that is (Matt 3:16, Mark 1:10, Luke 3:22, John 1:32).
Because of the breadth of optimistic reign over all of evil in this chapter, some want to regulate it all to the time of Christ's second Advent. But Christ's own ministry speaks to the certain establishment of all of chapter 11 in principle from the beginning of His first Advent and certainly from the beginning of His public ministry.
Jesus came - and, in principle, everything changed.