Actually, "heaven" will be the celestialized Earth, which will be changed to be a glory rivaling the sun. The WT idea that the Earth goes back to being a garden is absurd. What is everyone supposed to do, have an eternity of picnics and playing musical instruments, and reading Watchtower and Awake! magazines? The idea that God wanted Adam and Eve to live in a garden forever is absurd. He knew they were going to sin and He set them up for it. As one ancient writer stated, "before thou didst create them [man], thou didst know all their doings from eternity to eternity." (DST, Thanksgiving Hymn I: 7-13). That includes all of us.
This isn't the first populated world God created and it won't be the last. If anyone actually looks forward to spending a trillion years living in a stupid garden, they're welcome to it. (I imagine the second trillion years will be a bit boring.)
There are billions of worlds and billions of heavens, and veils. As one scholar of ancient scripture and history puts it:
Not only is God rendered invisible by the impenetrable veil of light that surrounds him, but he has purposely "placed veils between the worlds," that all treasures may be hid from those who do not seek them in the proper way. On the other side of the veil of the temple lay "the secrets of heaven," the celestial spaces which know no bounds, and all that they contain. The wilon (veil) quarantines this polluted world mercifully from the rest. "Beyond the veil are the heavens," and that goes for other worlds as well as this one....
We cannot even conceive of the worlds that lie beyond our own, or what this Earth will be like following its resurrection. The Earth, like us, was baptized by water during the flood and it will be baptized by fire when Christ returns. It will thus die and be resurrected and, like us, it will be resurrected to glory. It will, of course, be beautiful with lush vegetation, resurrected animals and buildings that will be beyond our ability to conceive, but it will radiate its own light. ""Eye hath not seen nor ear heard, neither hath entered into the heart of man the things which God hath prepared. ..." (I Corintians 2:9)
What most thrills the psalmist of Qumran as he sings of the bounteous fountain of God's hidden treasures is the thought that he is not only a beneficiary of God's plan, but was actually taken into his confidence in the making of it -- he was there! When Clement of Alexandria recalls that "God knew us before the foundation of the world, and chose us for our faithfulness," he is attesting a well-known teaching of the early Church [premortality]. The recurring phrase, "Blessed is he who was before he came into being," is not a paradox but refers to two states of being...."
We will be able to visit other worlds and other kingdoms throughout the Universe with instantaneous speeds, and no secrets will be withheld from us. Those who gain eternal life will be able to convert their bodies to pure energy, just as Christ did when He entered the buildings where the apostles were staying. And He ate fish and let them handle His body to show them that He was not an ethereal being, but that He was a physical being made up of pure matter. As the apostle Peter told Clement, "we say unequivocally that there is nothing bad about material substance."(Clem. Recog., IV, 23)
Concerning premortality, Jesus was asked of His disciples, "Master, who did sin, this man or his parents that he was born blind?" They knew that people existed before they were born, and they will exist after. Jeremiah was told that he was called and ordained before he came to this Earth (Jeremiah 1:5).
The entire JW eschatology makes me wonder why people would want to spend the next gazillion years on a lush green planet doing nothing but having family reunions. Nothing in ancient non-canonical Christian writings indicates soul sleeping or two classes of beings following the resurrection. All will be resurrected, but to varying degrees. None will be resurrected as spirits, because everyone already is a spirit, and they were spirits before coming to the Earth. The 144,000 are to be temporal judges, but they will gain eternal life and will be resurrected just as Jesus Christ was -- as physical beings of flesh and bone.