You seem to be contradicting your previous post when you said not all people would be in the New Jerusalem. I also think our concepts of God's timeline may be different. I believe the following:
1. God comes back for His church and gives them glorified bodies (
1 Cor 15:51-53).
2. Once God has His church with Him, He comes back with those (
1 Th 4:14-17) who are deemed worthy to reign with Him as kings and priests (
Rev 5:10).
3. 1,000 years occur with the Kingdom of Jesus being established in Israel. Satan is bound in a pit during this time. The Jews are the subjects of the Kingdom and those counted worthy from the Church Age help Jesus to administer His Kingdom (
Rev 20:4-6).
4. After the Millennial Reign, those who were not part of the 1st resurrection (and subsequently "slept" during the 1,000 year reign) awake and the white throne judgment occurs (
Rev 20:11-12). I believe those who "will sleep" during the reign will do so because their faith produced no works while they were alive, which is why they were judged by their works.
5. Those with their names written in the Lamb's book of life enter into Holy Jerusalem and those who don't have their name in the book are cast into the lake of fire (
Rev 20:15).
I have thought about why the gates will never be shut and my belief is so we can explore. Explore what you may ask? Whatever is outside the gates. The Bible doesn't explain much about what is outside the gates, but I'm seriously doubting the Lake of Fire is next door and accessible to visitors. Once this city is manifest, the invitations have all been sent and the roll has been established by the Book of Life. You're either in or you're out.
I have also thought about the leaves that are for the healing of the nations. In this place, the Holy Jerusalem, there is no pain/tears/death/sickness etc. I believe that the leaves of tree are correlated with the environment that produces the lack of negative (for a lack of a better word) conditions and emotions that people experience. Jesus ate after the resurrection in His glorified body (
Luke 24:42-43) and our bodies will be like His (
1 John 3:2). If Jesus ate in His glorified body, we will be able to do the same. The Bible does not give instruction on what, if anything, these bodies will need as nourishment. If they need anything, I believe it is found on this tree.
Do you mind posting the scripture reference to the "Who will the elect rule over", question? My first thought is that is referring to the Millennial Reign, but I'm not sure until I see the reference. My belief is, during the Millenial Reign where the Kingdom of Jesus is established in physical Israel, all of the nations will come to receive the Word of the LORD from Zion and those who have been counted worthy from the Church Age will help Him to administer His kingdom. Those who are not in this "Administration" will sleep for the thousand years. See
Revelation 20:4-6. I'd have to study a bit because it's been a while since I've dug in to this topic, but I can't recall ever studying scripture and feeling that anyone but God is going to rule in Holy Jerusalem.