Hi Darren,
Verse 17 tells us when this is.
Isa 65:17 "For behold, I create new heavens and a new earth;
And the former shall not be remembered or come to mind.
As David said it is the same setting as Rev. 21;
Rev 21:1 Now I saw a new heaven and a new earth, for the first heaven and the first earth had passed away. Also there was no more sea.
So this is speaking about the kingdom coming to the earth when Jesus Christ returns. But only the Elect Will be in spiritual New Jerusalem, there will be the whole physical world too.
I think these Scriptures are speaking of the way things will be at that time, both spiritually and physically.
Isa 65:20 "No more shall an infant from there live but a few days,
Nor an old man who has not fulfilled his days;
For the child shall die one hundred years old,
But the sinner being one hundred years old shall be accursed.
This verse is interesting, because we know "there shall be no more death" (Rev 21:4), as in physical dying. Babies will not die, nor someone who is old shall not die, they will fulfill their days, how? "For the child shall die one hundred years old," they will die spiritually to their carnal ways. If they are not overcoming... "But the sinner being one hundred years old shall be accursed."
Isa 65:22 They shall not build and another inhabit;
They shall not plant and another eat;
Maybe what this verse is saying is that in this world the poorer people work for the rich people and build them beautiful houses and such. But at that time, when Christ rules the world, things will be different. I think Christ will turn the tables on the rich, those who have lived their lives in wealth and decadence being served by those who are less fortunate.
Luke 14:11 For every one who exalts himself will be humbled, and he who humbles himself will be exalted.
When Christ rules people will not be subservient to the wealthy, because...
Isa 65:23 They shall not labor in vain,
Nor bring forth children for trouble;
For they shall be the descendants of the blessed of the LORD,
And their offspring with them.
Isa 65:24 "It shall come to pass
That before they call, I will answer;
And while they are still speaking, I will hear.
Isa 65:25 The wolf and the lamb shall feed together,
The lion shall eat straw like the ox,
And dust shall be the serpent's food.
They shall not hurt nor destroy in all My holy mountain,"
Says the LORD.
This is just what I am seeing in these verses. Hope it will be helpful to you in your studies
mercy, peace and love
Kat