In 2:11, 12, 17, 20, 3:7, 18, the refrain "in that day" (or "day of the Lord" once in 2:12) runs over and over these judgment sections. The judgments of Chapter 1 were followed with a vision of a glorious future in 2:1-5. The judgments of Chapters 2-3 are followed with another glorious vision of restoration and beyond in Chapter 4.
There are many "days" of the Lord and we will see that throughout this book as many nations are judged. But all foreshadow a particular "day." The debate is whether the resurrection of Jesus Christ is the hinge for that day in the middle of history, or whether that day is actually at the end of all history.
If the day of the Lord is something still to come then Jesus' first advent really only procured something for the future. But if the day of the Lord occurred 2000 years ago, then these visions of future glory in Isaiah can be understood to have been fulfilled in principle now with a "now and not yet" manifestation, like yeast working through a lump.
I believe Scripture contends for the latter interpretation. And I believe working through Isaiah will confirm this.