ANSWER: The simple truth that seems to elude the majority, is that there is a distinction between “sleeping in death” and death.
In that very same 15th chapter of Corinthians Paul explained to the unreasonable Corinthians how the resurrection works. He used an illustration of a grain of wheat and he explained that a shaft of wheat does not come into existence unless first the seed dies, so that the end result is a plant is produced and there is nothing left of the seed from which it came. The same is true with the heavenly resurrection. A spirit does not come into being unless first the anointed human dies.
In the case of those who die before Jesus’ parousia commences they must sleep in death – just as the billions of non-anointed persons who have died. As for the chosen ones who are living at the time of Jesus’ return they too must die but they did not go into a state of unconsciousness. Instead, upon their deaths they are instantaneously changed from flesh to spirit – “in the twinkling of an eye.” The “change” will leave behind a human corpse, but will produce an immortal and indestructible new creation.