Interesting concept and I would have agreed with you more a few years ago, but my view has been tempered since then. Here are my issues:
Judgment Day: Judgment Day happens after Satan is destroyed. Those who are judged get eternal life. Then those who are resurrected from the dead, everybody who lived good and bad, come back. But they are specifically said to no longer marry. After that death is destroyed forever. This suggests that earth would have reached population zero growth with everyone alive being granted eternal life. It is not likely they will be having more children at this point, one of the reasons is because of some of those children, not having been proven, would need to be put to death if they were unfaithful. Death is supposed to be no more. Further, as you noted, the earth would eventually run out of space. So there is no great need to find new planets for humans to populate. Though I'm not ruling that out.
The Joy of Space Travel: We all like the concept of exploring the universe I think. I thought perhaps once that was an indication that those on the earth would develop what it takes to explore the universe. But now I think that is not so necessary when you consider that 1,440,000 (the Bride Class) who are converted to angelic form will be able to explore space if they want. That is, space travel and exploring the universe is something the angels get to do. There may very well be other planets, thousands of them with life on them of all sorts, dinosaurs still roaming around, the whole bit. That would be fascinating. But that decreases the need for humans to go to those places. So I'm thinking now, maybe the vast universe, which can be traveled and enjoyed far more easily by the angels than man are meant for them, and while there are other planets that have animals and vegetation of infinite variety, it makes the earth something special to be the only planet with humans. Further, who is to say, like some think, that god won't grant the ability of all humans to become angels? You know a third of the angels did in fact defect from heaven. Some people think God will use the final number of those on earth to replace those angels. Keep in mind as well, that angels can materialize into human form if they missed being human, right? Angels have always had the ability to become "human" but not visa versa. So if you were an angel, you'd have the best of all worlds, not that anybody on the earth in human form would be bored being human. So I don't know. So I'm torn. Torn between the idea of eventually populating other planets in the universe with humans, and going through that whole Eden exercise again, or leaving well enough alone now that the population of earth has been "perfected" through all that trial and pain to get them to this state. There is the appeal of being unique and rare, letting the earth be the ultimate gem of the universe in every way. I feel that even if God has created animals and creatures on other planets that support that type of life, there would be no need to create humans.
The Origin of the Universe: Finally, based on the Bible, my feeling is that the vast universe was created for the purpose of the earth to have light and stars, and thus the universe is not really that old, but it appears to be. Basically, once Satan became corrupted and began causing problems in heaven the solution to resolve it was to kill him, obviously, along with the rebels. But that wasn't so easily done. Satan had crossed the line of rebellion psychologically and emotionally but not materially. Thus in a "put your money where your mouth is" challenge God created a situation where a material indiscretion with the penalty of death would allow Satan to sin and be condemned rightfully to death. Thus the earth and man and the possibility of SIN was created. This suggests that the idea of the physical universe didn't come up until the need to create the possibility of SIN in order to get rid of Satan. So the age of the universe per our logical perception of the light coming to the earth is trillions of years old, but since God could create the light retrospectively at the same time he created the universe, the stars are likely no older than the earth. In other words, when God created the universe, he created it already 800 billion years old from the beginning. Why not? God was being "creative". That's why he is called "The Creator." But with that view, that is, another more subtle original purpose for the physical universe, it seems that the focus of what is really going on is still actually in heaevn and not on earth. So the earth will either remain its own unique gem of the universe and the ultimate statement of God's physical creations, or at some point, he'll give everyone angelic abilities. But that is just speculation. But it will be up to God.
You have to consider it from God's point of view. At the point of the end of Judgment Day, the entire heavens and the entire earth are full of only those who love the Creator. At that point it is a perfect heavens and earth with everybody happy. Why introduce the possibility of rebellion and death again by more children being born? They'd all have to be tested in some way, and now Satan is gone. It wouldn't be the same. It would boil down to Jehovah deciding if he wanted more humans and angels to have the gift of life or simply keeping those who had proven their loyalty to God happy. One BIG happy family of angels and humans, but a finite family. The universe, after all, is not endless, but big enough to keep the angels busy exploring hidden treasures of God's creations throughout eternity.
Plus to fully enjoy the earth and humanity would take billions of years! Case in point, if you're living forever you'd have time to get to know every single human on the planet. So say there are 4 billion people who are perfect and living forever having been granted to partake of the tree of life? How could they all get to really KNOW each other? Well, how about a rotation schedule where every other year, you are matched with another human to live with them domestically for a year? At that time there will be no differences between male and female, everyone will be unisexual or androgynous, having equal aspects of both sexes sans the reproductive elements. So there will be sex, but no marriage or children. Even now, some humans are born with functioning organs of both sexes. So the entire human family will be like one big marriage. Even so, with a year off to do what you want and a year scheduled to be with a new human, it would take 8 billion years alone to complete that cycle.
Think about Christ in heaven with the Bride Class. They are all married to him. Do you think some of them might be jealous of the others because Christ is spending more time with one than the other? Well it might be the same way. Even if in heaven it could be instantaenous, that is Christ could be having a simulatenous individual marriage with each one rather than a group marriage, still it would seem Christ was giving you individual attention. But it could be the same way in heaven. That Christ will alternative living with each of the members of the Bride Class say for seven years each. With 1,440,000 individual members, it would take over 10 million years for that cycle. ADDICTED to LOVE and LIFE! Love can only be expressed by eternity because you never, ever want it to stop. It's just going to be glorious. But the more individuals you have, the more diluted the experience, so I think God knows where the perfect balance is for this sized universe.
But that makes it all the more important to make sure we get this once in a lifetime chance. See when those coming back on Judgment Day see all that is ahead for those who attain eternal life, they will be in torment over what they so foolishly threw away pretending to be grand and above it all. It will be like playing the same lottery numbers for years and years and never winning. Then one day someone comes by and distracts you one day, whatever it takes, and you end up deciding not to play the lottery that day, thinking you won't win. But, of course, that is the day your numbers hit! You would have been RICH! The jackpot was $800 million! How do you feel? You hate yourself and you hate the person who distracted you, especially when you find out they did it deliberately. Now you can only feel bad to the core your last minue alive. In the meantime, everybody else alive will feel they have won that $800 jackpot!
ONLY ONE ARCHANGEL: Finally, God only created one archangel. He could have created other angels directly, but that would not have made Michael/Jesus that unique. So God does understand rarity and uniqueness and he made someone who could understand as closely as possible what it is like to be God, a unique being, unlike anyone else. So in that regard, there is an argument about populating the entire universe with people versus allowing the earth to be unique. Plus those on the earth will have the unique experience of knowing what the world was like with Satan and imperfection. That heightens their thankfulness and sense of being alive. This was THEIR CHOICE. They had been to Oz and back and they know they've won the lottery. That level wouldn't be reached by those born in a perfect world, no more than all the angels appreciated being created in the perfect world of heaven. So God's point was made once and for all time.
So in conclusion, though I thought about god populating the vast universe, using humans from Earth, I'm now thinking probably not. Those coming out of Judgment Day have a special experience that makes it all the more important to be human and happy and faithful to God. Creating new people or angels that won't have the experience of reaching this level of happiness thus seems contraindicated. I think this was the big picture and for humans, the universe is meant to be looked at from a distance and admired, while they likewise explore live on this planet under the microscopic and even at the subatomic level to discover the majestic artistry of the Creator. We'll all be so absorbed with things to complete on the earth there just won't be any real interest to start new families in new places, though I'm not ruling that out. I think we need to think outside the box just a bit. Plus who knows what new capacities we'll have as perfected humans?
JCanon