Where will believers spend eternity?

From a Bible Literalist perspective there are two places where a person might go when they die: to heaven or to hell.

Mar 16:16 He that believeth and is baptized shall be saved; but he that believeth not shall be damned.

Rom 10:9 That if thou shalt confess with thy mouth the Lord Jesus, and shalt believe in thine heart that God hath raised him from the dead, thou shalt be saved. Rom 10:10 For with the heart man believeth unto righteousness; and with the mouth confession is made unto salvation. Rom 10:11 For the scripture saith, Whosoever believeth on him shall not be ashamed. Rom 10:12 For there is no difference between the Jew and the Greek: for the same Lord over all is rich unto all that call upon him. Rom 10:13 For whosoever shall call upon the name of the Lord shall be saved.

Joh 14:2 In my Father's house are many mansions: if it were not so, I would have told you. I go to prepare a place for you. Joh 14:3 And if I go and prepare a place for you, I will come again, and receive you unto myself; that where I am, there ye may be also.

Heb 10:34 For ye had compassion of me in my bonds, and took joyfully the spoiling of your goods, knowing in yourselves that ye have in heaven a better and an enduring substance. Heb 10:35 Cast not away therefore your confidence, which hath great recompence of reward.

Heaven is open to all those who acknowledge Jesus as Lord. When you accept Jesus as your King and Friend you become saved and can reap the promise of going to Jesus's Father's House Heaven when you die. This is salvation which mark 16 Romans 10 refer to and the recompense of reward which Hebrews 10 refers to.

Luk 16:22b the rich man also died, and was buried; Luk 16:23 And in hell he lift up his eyes, being in torments, and seeth Abraham afar off, and Lazarus in his bosom.

Those who fail to accept the Lord after hearing the gospel certainly go to the default location of all humanity hell. Even those who are "good" and who go to church many times.

Those who never hear the gospel and die "unreached" are an unknown the word does not say if by some supernatural way they hear the gospel upon death and are given the option to follow Jesus though many believe as such.

The Bible never speaks ill of heaven (or God). Many books have been written describing heaven by personal experiences or visions. From my group called Word of Faith a few are Heaven is for Real, Heaven: Close Encounters of the God Kind, Revealing Heaven and Within Heaven's Gates.

The Bible does describe people as being in hell and being tortured. Nothing positive is ever said about hell in the word. Select people have also visited hell. 23 Minutes in Hell is one example and I went to Hell are two examples.

Disembodied souls now live in heaven or hell.

We are confident, I say, and would prefer to be away from the body and at home with the Lord. (2 Corinthians 5:8, NIV)

Then he said, “Jesus, remember me when you come into your kingdom.” Jesus answered him, “Truly I tell you, today you will be with me in paradise.” (Luke 23:42-43, NIV)

After the final judgment their will be a new heaven and earth and the disembodied souls in heaven and hell will also receive new bodies. (Rev ch 19 & 20)

However, I admit that I worship the God of our ancestors as a follower of the Way, which they call a sect. I believe everything that is in accordance with the Law and that is written in the Prophets, and I have the same hope in God as these men themselves have, that there will be a resurrection of both the righteous and the wicked. (Acts 24:14-15, NIV)

The verse you mention is a different subject all together. Jesus was trying to explain spiritual things that could partly be comprehended by similar earthly things. However the deep things Jesus had to say about his being sent from heaven to the world to die and resurrect for the salvation of all men who believe does not have earthly references to refer to. In fact this deep knowledge of salvation can never be arrived at by a human ascending into heaven, into the region of absolute and eternal truth, so as to look upon it face to face. No man has ever done so. The only way this knowledge can be attainted is by the One who came from heaven. He alone through the incarnation is the one that descends and rises back into that eternal place who alone possesses that knowledge and declare it to men. By faith in Him and his death, we also rise to live with him, first the soul and then the body. Upon faith in this eternal son the descended and ascended back into heaven does one obtain life and knowledge. This was too much for Nicodemus to understand at the time as we was stumbling over smaller things such as the new birth which have its fruits seen here on earth and referenced to earthly things to help us understand it.

“You are Israel’s teacher,” said Jesus, “and do you not understand these things? Very truly I tell you, we speak of what we know, and we testify to what we have seen, but still you people do not accept our testimony. I have spoken to you of earthly things and you do not believe; how then will you believe if I speak of heavenly things? No one has ever gone into heaven except the one who came from heaven —the Son of Man. Just as Moses lifted up the snake in the wilderness, so the Son of Man must be lifted up. (John 3:10-14, NIV)