It has already happened once. Orthodoxy calls it the Harrowing of Hell.
Note: Christ was laid in an above ground tomb. Where is the heart of the earth?
(the realm of the dead) A term found 29 times in the NIV translation of the Bible.
Matthew 12:40
For as Jonah was three days and three nights in the belly of a huge fish, so the Son of Man will be three days and three nights in the heart of the earth.
1 Peter 3:18-20
For Christ also suffered once for sins, the righteous for the unrighteous, to bring you to God. He was put to death in the body but made alive in the Spirit. 19 After being made alive, he went and made proclamation to the imprisoned spirits— 20 to those who were disobedient long ago when God waited patiently in the days of Noah while the ark was being built. In it only a few people, eight in all, were saved through water,
Ephesians 4:8-10
This is why it says:
“When he ascended on high,
he took many captives
and gave gifts to his people.”
9 (What does “he ascended” mean except that he also
descended to the lower, earthly regions?
10 He who descended is the very one who ascended
higher than all the heavens,
in order to fill the whole universe.)
1 Peter 4:6
For this is the reason the gospel was preached even to those who are now dead, so that they might be judged according to human standards in regard to the body, but live according to God in regard to the spirit.
Romans 14:9
For this very reason, Christ died and returned to life so that he might be the Lord of both the dead and the living.
@RushMAN, if you would like to read please do. You might find it insightful or reject. Either way, it's imperative at least to me in a true sense to be able to come to common grounds even if is just on the basis of love itself.
There is scriptures in 2nd Corinthians 5:10-21, that is good to look at. The first verse says we stand at the judgement seat of Christ and are judged based on what we did with our life, good or bad. Then it later mentions that because of the Lord Jesus Christ who died on the cross for the sin of the world, all people are dead. The only way people are raised back to new life is their belief, on God, and the Lord Jesus Christ.
Who raises a person into a new life, and because we have a choice, we can either live in this new life or not. The judgement will be based on the choice of how we lived. Did we live in faith, and love others, or did we not live in faith, and hate others and never forgive them, even for their differences of opinions.
In my estimation that if we chose Jesus Christ we would be transformed into his light and his ways, that we would seek God in our lives, and try to even love our neighbors regardless of their distinguished beliefs.
It goes on to say, God reconciles the world unto himself. That to me says that God has saved all people from their sin in the world, through the blood shed of Christ Jesus, (1 John 2:2). So it seems to me, in my best estimation even though, I do not believe in the way of universalism anymore, yet that of total reconcilationism, that all people have been saved from their sin because of Jesus Christ.
It still leaves things up to God to decide by the judgement seat of Christ of what people have done with their life. We can find in John 5:29 about the two resurrections that are going to happen. One for the believer, and one for the unbeliever.
Now this is the confusion with universalism is that ALL are just going to go to heaven, but with no direct description of how this all plays out it's always seemingly convoluted in my opinion, though I respect my brothers who believe that way if that is what you desire so be it.
Referring back to the passage above about John 5:29 and the two resurrection we can see that believers, and unbelievers are both going to receive a spiritual body, (1 Corinthians 15 for more on that).
Now the most interesting thing about total reconcilationism, is that all of these people who pass away, whom are thus judged rightly by God, given a spiritual body that is pleasing to him, do not perish away (2 Peter 3:9), but all to come to knowledge of the truth (1 Timothy 2:1-4).
Where do they all go?
All people go to God. They are either able to enter the kingdom of God due to their faith, and love towards other people. (Revelation 22) The Kingdom Of God or Heavenly Jerusalem is where God and his Lamb (Jesus) dwell, and those who are able to bear his light will be able to because it says there is no night or moon there, all the light emulates from God. Though there is an outside part to this city, IE where unbelievers, who are not able to bear the light reside. This is where unbelievers who are judged based on the life they have chosen, and they desired nothing to do with God, or to love others, or have faith.
Can people come into this Heavenly Jerusalem that are outside the Gate? Who are far out of proximity to God?
No one can say, though it doesn't never say the gates close these people off forever.