So when, do people think was or will be the fulfilment of versions Is 11.8 and 65.20
11:8 When, However, is this change to appear? In answer it should be noted that Isaiah has emphasized the fact that the Messiah is the Prince of Peace. When the Messiah has completed His Messianic work, peace is introduced into the hearts of men, and insofar as men are true to the principles of peace which they have received from the Messiah, so far do the blessings herein depicted obtain. In its fullness, however, this condition will not be realized until the earth is covered with the knowledge of the Lord, and that condition will only obtain in the new heavens and the new earth wherein dwelleth righteousness. "Whenever there is sin," says Bracker, "there is lack of peace. Only where righteousness reigns, is there peace." For this reason the condition herein described cannot apply to a supposed millennium. Advocates of a millennial theory maintain that even during the millennium there is sin, for after the millennium the nations will again gather for battle. The picture before us, however, is one in which there is no sin, but in which the fullest manifestation of peace is to be seen. We read these words with grateful hearts for we know that one day we too shall enjoy these blessings in their fullest sense.
Now as to 65:20...
The CONTEXT is set in v. 17, "
For behold! I am about to create new heavens and a new earth and the former things shall not be remembered, and they shall not come up upon the heart. 18
But rejoice and be glad unto eternity in that which I am about to create for I am about to create Jerusalem a joy, and her people a rejoicing.Thus, what follows pertains to the "new heaven and new earth" and they shall continue for "eternity", in contrast to a fixed time of 1000 years.
v. 20 The description now introduces particulars of the Messianic kingdom, stressing the longevity of those who will belong to that kingdom.
From there may refer to Jerusalem, the thought being that
There will not be from there (i.e., taken away from there by death)
a suckling with respect to days. Thus, death will not take away from there (i.e. from the Jerusalem of the Messianic age) one who is merely a suckling child as death is now wont to do. Nor will the elderly man who has not yet lived out the full span of life meted to him be taken away by death as is now the case.
In the second part of the verse the opposite truth is express. The youth who is one hundred years old will die, i.e., when one dies at the age of one hundred, he shall be regarded as merely a youth, the implication being that he had yet far more life to live. Likewise, when death cuts of a sinful man, it does so when he has lived a hundred years. Men will die, and death is a curse and when that curse comes as a punishment for sin, as it does even to God's people, the sinner will be a hundred years old. Thus, one of the blessings of the new age is that of longevity. Basic to this promise is probably the conception already expressed in Genesis 53. The conditions of Paradise are to be restored, but the new age will surpass Paradise.
Or, if someone can suggest other threads to go to for answers to this that would be great.
I get the impression that you have confined your reading of things on The Highway to just this Board. IF that is correct, then I would like to refer you to the main website
HERE, where you will find 1600+ books, articles and sermons on varied subjects. More specifically, we have a whole section dedicated to Eschatology which you can find
HERE.