I think that the WT is perhaps the only organisation, their description, that teaches the 2 tier system .
Yes the Bible says that eventually the earth and the heavens will be destroyed after the devil has been imprisoned for a 1000 years . During this time what appear to be martyrs " those who had been beheaded for their testimony about Jesus " will reign with Christ . Interestingly the wording is " they CAME to life and reigned with Christ " Rev 20
Ch 21 starts with " then l saw a new Heaven and a new earth for the first Heaven and the first earth had passed away. and there was no longer any sea "
I know that some Bible scholars think that the sea refers to the sky so now Heaven and earth are merged
Then we are told that God's dwelling place is now among the people and He will dwell with them in the new Jerusalem.
Ch 22 says that from the throne of God and of the Lamb a river of the water of life will flow and on either side of the river will be the Tree of Life
This sounds like maybe Eden restored. So the implication seems to be that the New Heaven and New Earth will be one and ALL " the saved " will be together with God.
So how does the WT get the teaching that some stay on earth for ever and 144,000 go to Heaven ? That is also where they lose anyone with any Bible knowledge. I've queried this with JWs and basically the answer is " It's what the Org. says "
So yes a thousand year reign on earth but then it all changes.
I can't say that the WT is the only faith group that teach that some people will live eternally on this earth restored to perfection but l know that not many do .
Jan