What does Revelation 21: 8 means when it says that the wicked will be consigned to the fiery lake of burning sulfur? Are the souls to be punished there eventually going to vanish?
The meaning of Revelation 21:8 is that those who rebel against God and refuse to accept his love and salvation will go to hell. Hell is a place of separation from God and of suffering. The exact nature of that suffering is not clear. Obviously, Revelation uses symbolic language, both to describe heaven and hell. What cannot be doubted is that the Book of Revelation makes it clear that there will be a judgement day at the end of time and that every single soul will be judged and after that will either go to a place of blessings–heaven–or will go to a place of shame, suffering and separation called hell.
Revelation as well as Daniel 12 and many other passages imply that both heaven and hell will be eternal. Revelation 20:10 talks about suffering “day and night for ever and ever.” Jesus called the final state of those saved by him “eternal life” in many places. The Bible clearly describes both heaven and hell as a final, eternal state. If this is true, one will have to present a strong argument to support a claim that the blessings are forever, but the suffering is not.
Some Christians believe that the suffering in hell will be for only a limited amount of time, after which souls will be eliminated. It is hard to support this view from Revelation alone, but a fairly good case can be made that the suffering in hell is not eternal, but the result–suffering followed by annihilation–is eternal. I am skeptical of this view, but some Bible teachers I generally respect hold to this view. In fact, we have a power point at the web site (see the front page) by Douglas Jacoby in which he defends the claim that the judgement of those who reject God is eternal, but that the suffering itself is only temporary. The article also includes his notes. He will soon publish a book titled “What Happens When We Die.” It will be available at www.ipibooks.com
I do not agree with this teaching, but will admit that I might be wrong. You should study the scriptures and read what faithful Christians on both sides of this issue have to say and reach your own conclusion.