I’ll offer a less-popular take (but what fun would it be to repeat things that have already been said on related questions?). I suggest that the spirit is not dormant between death and the resurrection, but does indeed remain conscious.
The Bible frequently refers to the dead as “asleep”. This is clearly metaphorical—even without the advent of modern medicine people realized that there was a difference between being asleep and being dead. This is demonstrated by Luke 8: 52-53:
52 And all wept, and bewailed her: but he said, Weep not; she is not
dead, but sleepeth.
53 And they laughed him to scorn, knowing that she was dead.
But “asleep” is a useful metaphor for death and the resurrection—sleep isn’t permanent—you will wake up.
To take it one step further, though, and argue that therefore the dead have no consciousness is I believe unwarranted. Not only do those who are sleeping have continued cognitive activity (i.e. dreams), but there are numerous instances in the Bible where people experience visions—and they are conscious of the experience.
Paul provides a useful example:
I knew a man in Christ above fourteen years ago, (whether in the body,
I cannot tell; or whether out of the body, I cannot tell: God
knoweth;) such an one caught up to the third heaven. (2 Cor 12:2)
Paul is uncertain whether his body was left behind or not…but either way, Paul had no issue with the idea that someone could be conscious without a body.
The word commonly translated as “Spirit” in the New Testament is “pneuma” (and variations thereof) which literally means “breath” (see here).
This brings substantial light to the statement in Genesis 2:7:
And the Lord God formed man of the dust of the ground, and breathed
into his nostrils the breath of life; and man became a living soul.
God supplied something—something which is rendered over and over again in the Bible as “Spirit”—and that gave man life. Many have concluded that humans have a spirit and a body—that the spirit dwells in the body while the person is alive, and departs the body at death.
This would make for a very straightforward interpretation of these passages:
…Stephen, calling upon God, and saying, Lord Jesus, receive my spirit.
And when Jesus had cried with a loud voice, he said, Father, into thy
hands I commend my spirit: and having said thus, he gave up the ghost.
They knew their body was dying but their concern was for their spirit - because they believed their spirit was going somewhere.
That “give up the ghost” is a euphemism (in English, not Greek) for death implies that this is a commonplace interpretation: something of a spiritual nature is leaving the body.
See also discussion of these ideas in Dave’s post here, and as Nihil Sine Deo has observed:
The body is a housing for the spirit. Jesus preexisted His birth in
the human body, known as the incarnation.
“Now I want to remind you, although you once fully knew it, that
Jesus, who saved a people out of the land of Egypt, afterward
destroyed those who did not believe.” Jude 1:5
“Jesus said to them, “Truly, truly, I say to you, before Abraham was,
I am.”” John 8:58
The apostles believed a spirit could do things after death
The fact that the disciples in Luke 24 had to be told that Jesus was not a ghost/spirit presupposes the existence of the spirit—and that the spirit does not become dormant at death:
But they were terrified and affrighted, and supposed that they had
seen a spirit. (Luke 24:37)
Jesus then confirms that spirits are a real thing:
Behold my hands and my feet, that it is I myself: handle me, and see;
for a spirit hath not flesh and bones, as ye see me have. (Luke 24:39)
And the word used in verse 39 for spirit is none other than “pneuma”.
The dead are conscious somewhere
Passages like the below have had people doing theological somersaults for centuries, but that’s a matter for SE-Christianity. The Bible does speak of conscious activity by the dead. It may not be clear where they are, but it is clear that they are portrayed as conscious agents:
Multiple passages speak of the message of Jesus being taught to the dead.
1 Peter 3: 18-20:
18 For Christ also hath once suffered for sins, the just for the
unjust, that he might bring us to God, being put to death in the
flesh, but quickened by the Spirit:
19 By which also he went and preached unto the spirits in prison;
20 Which sometime were disobedient, when once the longsuffering of God
waited in the days of Noah, while the ark was a preparing, wherein
few, that is, eight souls were saved by water.
1 Peter 4:6:
For for this cause was the gospel preached also to them that are dead,
that they might be judged according to men in the flesh, but live
according to God in the spirit.
Some understand Isaiah 9:2 to be teaching the same principle.
Note that these passages are not only indicating that the dead are conscious in that they are being taught, but they also speak of conscious activity by Jesus between His death and resurrection. They are spirits, and they are not dormant.
These passages are also interesting because they speak of both the righteous and the wicked.
The Thief in paradise
And Jesus said unto him, Verily I say unto thee, To day shalt thou be
with me in paradise. (Luke 23:43)
This passage has also been rendered as “in the world of spirits”.
And in Revelation 6:9-11, the passage cited in the OP, the dead here are speaking, being spoken to, and are being given robes. This suggests that not only are they conscious, but their disembodied spirits have substance.
I’ll cite just one more passage—this one from Clement of Rome, a man who was taught by the apostles:
There was Peter who by reason of unrighteous jealousy endured not one not one but many labors, and thus having borne his testimony went
to his appointed place of glory.
By reason of jealousy and strife Paul by his example pointed out the prize of patient endurance. After that he had been seven times in
bonds, had been driven into exile, had been stoned, had preached in
the East and in the West, he won the noble renown which was the reward
of his faith,
having taught righteousness unto the whole world and having reached the farthest bounds of the West; and when he had borne his testimony
before the rulers, so he departed from the world and went unto the
holy place, having been found a notable pattern of patient endurance.
(1 Clement 5:4-6)
Here we have an apostolic father who is suggesting that although Peter & Paul have not yet been resurrected (see 1 Clement 24:1 & 26:1), they are already in a better holier place and have already received some form of glory. Clearly Clement believes there is something between death and the resurrection.
So I went ahead and challenged a popular view; I’d better wrap this up as some are itching to down-vote this post to Hades (pun totally intended), but my conclusion is this:
- Humans have (at minimum) a spirit and a body
- The spirit departs the body at death
- After death the body decays but the spirit is not dormant
- Spirit and body come together at the resurrection
I understand the context of the question--including the relevance of other questions this site was discussing when this was asked--to be an inquiry as to whether or not the dead are conscious. My answer focuses on this angle.
This passage (and others) could certainly be used to engage in a discussion of the relationship of the meanings of the words ψυχή (soul) and πνεῦμα (spirit). I do not understand this to be the intent of the OP's question, so I have not addressed it in my answer.
Sometimes soul & spirit are used interchangeably, sometimes they are used distinctly. A more extensive discussion of these words would be more appropriate for a separate question.