For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
There is no "unforgivable sin" on this side of the cross including the sin of unbelief. The cross and Christ's shed blood was the means by which ALL sin WAS forgiven.
2 Cor 5:19
"To wit, that God was in Christ, reconciling the world unto himself, not imputing their trespasses unto them; and hath committed unto us the word of reconciliation."
Col 1:14
"In whom we have redemption through his blood, even the forgiveness of sins:"
Col 2:13
"And you, being dead in your sins and the uncircumcision of your flesh, hath he quickened together with him, having forgiven you all trespasses;"
Col 3:13
"Forbearing one another, and forgiving one another, if any man have a quarrel against any: even as Christ forgave you, so also do ye."
Eph 4:32
"And be ye kind one to another, tenderhearted, forgiving one another, even as God for Christ's sake hath forgiven you."
Forgiveness was universal and complete when Christ gave His life on the cross. What remains is ones belief for salvation.
Rom 3:23-26
"For all have sinned, and come short of the glory of God;
24 Being justified freely by his grace through the redemption that is in Christ Jesus:
25 Whom God hath set forth to be a propitiation through faith in his blood, to declare his righteousness for the remission of sins that are past, through the forbearance of God;
26 To declare, I say, at this time his righteousness: that he might be just, and the justifier of him which believeth in Jesus."
Sadly, hell will be filled with forgiven souls.