4 For it is impossible to restore again to repentance those who have once been enlightened, who have tasted the heavenly gift, and have shared in the Holy Spirit,
5 and have tasted the goodness of the word of God and the powers of the age to come,
6 if they then fall away, since they are crucifying once again the Son of God to their own harm and holding him up to contempt.
To the point
Once Saved Always Saved??? it would seem as though perhaps not by this passage. If anything it does point the the perfect sacrifice as being all sufficient. You cannot stand against God and in that you cannot stand against those who are "saved" as in persecution.
If anything can be gleaned from the book of revelations it is that some people are judged in this world, "saints", and those who are judged later, at the second coming. It could be said that the "saints" are saved; they are not in contempt of God and if they are they are dealt with. Everyone else might be as deserving of sainthood or being saved but they have not been judged yet. That may be a good thing, it may be a bad thing. It is through Miracles, signs and wonders that saints, disciples, are known and they are given to further the word of God (ie everything after the Gospels).
Peter, Cephas, after the Crucifixion became the head of the Church. He was put in jail. You cannot put the Church in jail and be saved. The guards did not know that Peter was a man of God. He did miracles and they then knew that he was. Likewise there are believers who proclaim their belief. These people cannot be persecuted. To do so is to hold Christ in contempt.
Personally, I believe that there is no time to make amends when the kingdom of God has come up someone who is in contempt. I say that I believe this because there is no way of truly knowing what Judgment Day will be like and what ruler we will be held to. If you think that it will be the Bible alone then you obviously didn't read it in the first place.
There is the notion that any sin is heinous to God and he see us all as wicked. Christ suffers hell for us as punishment redeeming us of our sins. This is not typically a disputed concept. What is in dispute is what it takes to be someone of Christ. John 3:16 says anyone who believes in his name. On the surface is seems like a one time thing like registering to vote. The name Jesus is an English word. The belief is something more then a verbal or internalized affirmation. Who he was, who he is and what he died for and why he died bring us closer to him. Part of that is that you do not hijack the true and go around doing un-Christ-like things in his name, etc. These people who pervert Christianity will suffer the deepest depths of Hell.