Second, Isa. 65:20:
“No longer will there be in it an infant who lives but a few days, or an old man who does not live out his days; for the youth will die at the age of one hundred and the one who does not reach the age of one hundred will be thought accursed.”
The premillennial view takes this verse literally and describes death as a reality during the millennium, but not the arrival of the eternal new heavens and earth, though some might want to argue that the millennium is a second inaugurated fulfillment of new creation (the first being when one is regenerated as Christian, e.g., 2 Cor. 5:17), which is then consummated in the eternal new creation, after the so-called millennium.
However, there is no other evidence in the NT for a second stage of inauguration of the new creation. In contrast to the premillennial perspective, the amillennial view can affirm two interpretations of this passage:
Isa. 65:20 is a figurative way of referring to along, indeed, eternal life, since all of 65:17-25 is clearly about the eternal new heavens and earth, as 66:22 also bears out. If this is true, then the broader context of eternal new creation surrounding 65:20 makes it likely that this verse is to be taken figuratively. It is extremely difficult to say that 65:17-25 is about the millennium and that 66:21-24 is about the eternal new creation. If a premillennialist were to affirm that both 65:17-25 and 66:21-24 are about the millennium, it would contradict Rev.21:1, which applies Isa. 65:17 and 66:22 to the destruction of the old cosmos and the replacement of it with an eternal new creation (likewise Isa.65:17 is applied to the passing away of the old earth in Rev. 21:4).
In the same way, 2 Pet. 3:13 applies Isa. 65:17 and 66:22 not to a millennium, but to the eternal “new heavens and new earth.” Furthermore, Isa. 66:24 appears to refer to the beginning of eternal punishment, which would correspond antithetically with an eternal new creation in vv. 22-23 (where references to eternal blessings are started). Also, the second part of Isa 65:17 says, “the former things [of the old creation] shall not be remembered or come to mind.”
But if this refers merely to a millennium on an old (but renewed) earth, then the fact that death will occur during the millennium (according to the premillennial view of 65:20) and again when Christ’s human enemies are defeated at the end of the millennium appears to contradict the promise in 65:17b that “the former things” of the old creation “shall not be remembered or come to mind” Indeed, the worst feature of the old creation—death—will “come to mind” during the millennium.
Or, as an alternative possibility that is also consistent with an amillennial view, Isa. 65:20 is about the inaugurated stage of the new creation (the fulfillment of which is noted in 2 Cor. 5:17) and refers to the idea that physical life is not eternal in the inaugurated phase of the new creation.
-G. K. Beale with David Campbell, Revelation: A Shorter Commentary, 447-448.