Homosexuality does not keep someone out of heaven any more than any other sin does. All sin keeps us out of heaven. As sinners, our natural state is separation from God (Isaiah 59:2) and as a result, we all ought to face judgment. That judgment is to be excluded from heaven where God dwells. This is because God is holy and in him, there is no sin. God is too pure to look upon sin with favor.
- Habakkuk 1:13, "our eyes are too pure to approve evil, and You can not look on wickedness with favor. Why do You look with favor on those who deal treacherously? Why are You silent when the wicked swallow up those more righteous than they?"
- 1 Peter 1:15–16, "but like the Holy One who called you, be holy yourselves also in all your behavior; 16 because it is written, “YOU SHALL BE HOLY, FOR I AM HOLY.”"
Homosexuality is a sin like adultery, lying, stealing, lust, coveting, etc. All sins keep us out of heaven.
- Leviticus 18:22, "You shall not lie with a male as one lies with a female; it is an abomination."
- Leviticus 20:13, "If there is a man who lies with a male as those who lie with a woman, both of them have committed a detestable act; they shall surely be put to death. Their bloodguiltiness is upon them."
So, homosexuality is a sin and sin separates us from God (Isaiah 59:2). Furthermore, people are damned because they don't trust in Christ. The sacrifice of Jesus on the cross is the only way that our sins can be forgiven, not just a sin of homosexuality, but all sin.
Know one sin keep us out of heaven as though the one sin is more dangerous, or worse than another. All sin is a form of rebellion against God, a lack of holiness that separates us from him and keeps us out of his presence.