The curse of death pronounced upon Adam has not been lifted. We all WILL die. Even Jesus was not an exception.
To understand Hebrews 9:27, one must understand:
1. The difference between dying and perishing.
2. Know what First Birth, First Death, Second Birth and Second Death are.
Dying and Perishing
When God sent His only begotten Son, was it for the purpose of preventing the world of mankind from dying? No! John 3:16 says from "perishing."
If one perishes they cease to exist; even as a dead person. Recall that the first man Adam existed in two forms: As a dead soul and when God breathed into his nostrils he became a living soul. Yet, Adam existed. Existed where? In God's memory. (Book of Life).
If a person dies, they have not perished because they exists in God's memory and will be resurrected. (John 5:28-29)
So we all DIE once.
First Birth, First Death, Second Birth and Second Death
The Bible at Revelation 20:14 speaks of something called The Second Death. This implies that there must be a First Death. If there is a First Death, there must be a First Birth. If there is a First Birth, there must be a Second Birth.
All ever born on earth have a First Birth. We all have a biological mother and father. Adam and Eve were exceptions. God created them. All on earth die. This is our First Death. There is no escaping it.
Now what happens on the other side of our First Death?
Jesus spoke about it with the Pharisee Nicodemus and Nicodemus did not understand him. Jesus used the expression "Born Again."
Born Again implies that a person had a first birth. How can a person be born again unless they were first born? That was essentially what Nicodemus did not understand. Yet, what Jesus was referring to when he spoke of being "Born Again" was being born again from the dead: The Resurrection.
When a person is first born and they take their first breath, what that person has standing inevitably in front of him is an eventual death. (first death)
Upon being resurrected (born again) a person has a Second Birth. At ones resurrection what now stands in front of the person? Another literal death? No! What stands in front of him is the prospect of "perishing" or removed from God's memory. If one is not in God's memory, that person does not exist, not even as a dead person. This perishing is called The Second Death which is the Lake of Fire at Revelation 20:14.
The Lake of Fire (Second Death) is a symbol of nonexistence. Anything placed in The Lake of Fire ceases to exist; it is out of God's memory.
The Second Death (Lake of Fire) can be likened to taking a piece of paper and throwing it into a literal fire. The paper is consumed and ceases to be. It cannot be restored back to paper. It is gone! It ceases to exist.
The Second Death (The Lake of Fire) is not a literal place. The reason why this is certain is to look at what is thrown into it. Death itself and Hell itself are thrown into it. One cannot literally burn death and hell. That death and hell are thrown into the Second Death (The Lake of Fire) is another way of saying that both death and hell will one day "be no more." They will cease to exist!
Rev 21:4 confirms this as it says, "... and death will be no more." Why is that? Because we are previously told at Rev 20:14 that death was thrown into the Second Death (The Lake of Fire).
So yes, we ALL will die once. We ALL will experience a Second Birth (resurrection as promised by Christ). But at our resurrections we face the judgment of perishing (Second Death) if we PURPOSEFULLY and WILLING sin against God WHEN we are FULLY KNOWING (knowledgeable). When we are Fully Knowledgeable (knowing good and bad) then there is no more forgiveness for sin. The sin we commit when we are fully knowledgeable knowing good and bad is what is called the "unforgivable sin" or "the sin that cannot be forgiven."
No one today can possibly commit this type of sin because we "DO NOT" know good and bad. Jesus asked forgiveness for those who persecuted and executed him. Why? Because they DID NOT KNOW what they were doing. Their bad act was forgiven.
Any bad act anyone commits today will be forgiven because WE DO NOT KNOW WHAT WE ARE DOING.
Yet a time will come when Christ will teach ALL resurrected God's righteousness (the knowing of good and bad). This will take up to 1000 years during his paradise rule over the earth.
By the time his 1000 year kingdom ends, no human on earth will be without excuse. That time AFTER Christs rule ends will be a time of faithful endurance as Satan will be released upon ALL of mankind and will mislead them. An angel will come with a message and awaken the misled. (Rev 14:6) Those who do not respond to that message will do so knowingly and defiantly. They will be without excuse. That is what is called the sin that cannot be forgiven. Christ can no longer ask the Father in our behalf in those future days, "Father, forgive them for they do not know what they are doing? All of mankind will one day know what it is doing and thus there cannot be forgiveness for sin anymore.
The third and last World Order is of God. There will be no others.