For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
The sitting of the Roman senators was called' the gate'. That was the Roman political structure where laws and decisions were made. When Jesus mention the word ' church', this word original was not a religious term as we currently think in the 21st century, it was the political term. As well said that it means the assembly of the called ones. Or it is the assembly of the senators in today's language. When Jesus said the gates of hell will not prevailed against the church, He was talking not about death but about systems of the world which are contrary to the kingdom of God. He was predicting persecution which was coming upon the church like 70AD, like the dark ages which tried to destroy the true church until God raised reformers. The biggest thread to the church is not physical death but is secularism, humanistic and new age belief. That's why Paul said to live is Christ but to die is gain. During persecution many believers accepted death with joy. We must also remember that Roman kings were perceived as gods.
Gates of hell has different levels according to our present focus. Yes it can be a hole in the ground known as a grave, and the adversary may have power to kill in respect to the first death. Or it could mean a place where a soul is kept in turmoil until the second resurrection, if he is not called in the first. I think the most profound meaning is when the soul is "tried", baptized by fire. In Mark 9:48 Jesus refers to this. This is the lake of fire which will consume all adversaries from which there is no deliverance except by faith in God's love. This is the baptism Jesus prayed to be delivered from. He was greatly straightened as to sweat blood while pleading for deliverance, for even "his" faith would be tried. He was saved by having "known" how much God loved him.
Thus he quenched the potential of being cast into outer darkness. We will know God's love when we are raptured by being one, knowing his eternal "oneness". After having being one we will come back to time were we are now, separated. Then we will be tried by fire and all who know that they have been known will have enough faith to quench the holy terror of being torn into outer darkness at "god speed". Jesus said ,"I have not known you, be cast out into outer darkness", and this to people who thought they were saved. We are only saved by being known, "one with god", and the right for us to be one was given to God by Jesus, as he tipped the scales of righteousness in our favor, in that while we may still have our demons in this present time, if we call to God in Jesus name, God has the right to make us know his holy love. For anyone to think that knowing God's Holy love isn't being "raptured" knows not. Jesus said "All shall be salted". The only way to survive the "salting" is by faith in God's love, being "one" as Jesus prayed we would be. Think about this a second, when he comes there shall be as lightning from the east to the west. What if this lightning is unbelieving souls being transformed into living fire, cast into outer darkness, literally. As Einstein postulated, travel at the speed of light and time stops. This is the eternal second death from which there is no resurrection, the power of hell as it rips you inside out in holy terror. Our soul is the gate, the matrix. If our soul has been Heaven's gate, one with god, the second death shall have no power over us and we shall be delivered, as by faith in the love of god, in Jesus name.
Amen