Paul goes to a great extent to explain the mystery in 1 Cor. 15. The return of Christ is first mentioned in verse 24. The body of his message is to explain and debunk the teachings of the Saducees. The Saducees believe that there is no spirit, no angels, nor resurrection… see Acts. 23:8. So here in this passage Paul is explaining that we indeed have a spirit body and a Earthly/natural body. Often Paul discusses this fact in other Scriptures, “to be absent from the body is to be present with the Lord.” There is no need for a Earth suit in heaven. Yet so many miss the nature of the mystery that Paul is explaining. The mystery is not about the rapture (being caught up), but rather about the resurrection of the dead (see vs.44), and what happens to the Earth suit (physical body/ natural man).
In Acts 2 we are informed that Jesus natural body did not become “corrupted” in the grave. In other words it didn’t rot and decay. This was prophesied in the Old Testament. So we are made to understand that Paul is talking about the dead saints who’s bodies have become corrupted by rotting and decaying. Paul is stating that we will not all “sleep.” This means that we will not all come to rest in the grave by dying. Those who are alive (and remain) will change in a moment from mortality to immortality. This is the exact opposite of what happened to Adam at the fall when he sinned. He changed from immortality to being mortal. Death entered into the World through sin. Prior to sin Adam’s “Earth suit” could not die.
Paul calls this event the “resurrection of the dead.” He also informs us that the dead saints will again get new natural bodies that cannot be corrupted, rot, or decay. This is the mystery that Paul is referring to in this passage. The reason that the dead saints will need a new physical body is because Jesus is not going to rule and reign for 1000 years on Earth. Without a natural body, the dead saints would be disembodied spirits running around at this time with no Earth suit.
John informs us in Rev. 20:4,5 that those who get martyred for not taking the Mark of the Beast will be resurrected at the FIRST resurrection. 1 Cor 15:42-54 speaks of this same first resurrection.
Acts 1:9-12 informs us that Jesus will return in “like manner” of that He left. He left from the Mount of Olives to the sky/clouds to heaven. If He returns in “like manner” then He will come from heaven with all His (dead) saints to the sky/clouds (1 Thess. 4:16,17, Matt. 24:29-31 where we meet Him in the air) to the Mount of Olives (Zech 14:4,5 with all of His saints).
Earthly bodies never go to heaven. When John was told to “come up here…” he was immediately in the spirit…. Rev. 4:1,2. At the time of the resurrection we will be changed, but the word “glorified” bodies are not used by Paul to describe our new Earth suits (natural bodies).