Rev 22: Outside are the dogs and sorcerers and fornicators and murderers and idolaters, and every one who loves and practices falsehood.
Seems this contradicts the earlier statement that all not written in the book are thrown into the lake of fire:
 And I saw the dead, great and small, standing before the throne, and books were opened. Also another book was opened, which is the book of life. And the dead were judged by what was written in the books, by what they had done.
 And the sea gave up the dead in it, Death and Hades gave up the dead in them, and all were judged by what they had done.
 Then Death and Hades were thrown into the lake of fire. This is the second death, the lake of fire;
 and if any one's name was not found written in the book of life, he was thrown into the lake of fire.
So apparently the dogs, etc. outside the city gates were written in the book- otherwise they would be already in the lake of fire.
This proves that the wotld will remain imperfect according to scripture.
In addition, the sea is gone along with all the creatures therein. Seems that God does not have much use for fish and dogs. How about women?
Then I saw a new heaven and a new earth; for the first heaven and the first earth had passed away, and the sea was no more.
My interpretation of these passages is that what is being described is heaven- the heaven that already exists. Earth had passed away for John and heaven was new for him.
It describes a two-fold aspect of heaven: the inner city where the really spiritual will stay with God and an outer heaven, outside the gates of the city, populated by people who are not yet spiritual and honest enough to be with God.
My belief is that these will get to try again in new earthly lives, in agreement with all the religions on this planet except Islam and Christianity.
I believe this an ongoing process- not one that is about to happen at some time in the future to us on earth. It actually happens all the time once any of us die. We are first put in the sea of death where the vulgar aspects of us are stripped away. From thence we are judged and if there is enough left of us we get into the city of God; and if not enough we end up outside the city and are soon born again.
Proof that it is already happening is the statement of Jesus that it will all come to pass before his Apostles die. That was almost 2000 years ago. Jesus cannot be wrong. So all scripture must be understood in the light of his prophecy. Even the Rev book says the same thing.
So do not expect great changes on earth. The great changes have already come to pass.