Just prior to this scripture, in Revelations 6, it says,
"[9] And when he had opened the fifth seal, I saw under the altar the souls of them that were slain for the word of God, and for the testimony which they held:[10] And they cried with a loud voice, saying, How long, O Lord, holy and true, dost thou not judge and avenge our blood on them that dwell on the earth?[11] And white robes were given unto every one of them; and it was said unto them, that they should rest yet for a little season, until their fellowservants also and their brethren, that should be killed as they were, should be fulfilled."
The only ones described with white robes were those who were martyred for Christ. I don't think it specifies which time period they were killed, so they could also include those who were slain throughout the ages for the testimony of Jesus Christ. However, we do know from this scripture that more are to be killed during these last days.
Based on Revelations 12, there will be 3 classifications of believers:
1) The man-child who is caught up into the thrown room of God to escape the devil (144,000),
2) The woman who flees into the wilderness and is protected by God for 3 and 1/2 years, and
3) The remnant of (her) seed, who is persecuted and martyred for their testimony in Christ.
All the others fall away from the faith, which to me is described in Revelations 12:4- "And his tail drew the third part of the stars of heaven, and did cast them to the earth:"
Many people use this scripture out of context to describe angels falling on the side of Satan to become demons. There is no scripture to support this notion. Also, in the context of the Book of Revelations, which speaks of the future, it is quite obvious that the application of this scripture to describe angels defecting to Satan's kingdom is in error. It is rather clear in Revelations 12 that Satan is going after Christians. It is also noted that Michael and his angels confront Satan in verse 7, which is after his tail drew down a third of the stars in heaven in verse 4. Chapter 12 of Revelations describe both Satan's defeat and Satan's triumph and slaughter of at least a portion of God's people.
2Thess.2:[3] Let no man deceive you by any means: for that day shall not come, except there come afalling away first, and that man of sin be revealed, the son of perdition;
(The words "falling away" simply means that some have fallen away from the faith). In my interpretation is that their place in heaven is no more.
Ephesians 2:6- "And hath raised us up together, and made us sit together inheavenly places in Christ Jesus:"
One of the biggest questions that Christians face today is "What group are you going to be in? The man-child, the woman, the remnant, or the fallen away? I hope it's either one of the first 3.