If the thing keeps running its course, they will go to hell. However if the man continues to perpetuate immoral thoughts, holding them in himself, and giving them freedom, eventually the protection of God will be removed, and occasion for sin will arrive and the deed will be done. There is no doubt about that. But He wasn't saying that the minute you think it you are finished, He was making a relational statement. The sentence against the deed is not executed quickly.
Injustice rolls over everyone.
If a person makes a bad response to injustice then he will progressively become a suspicious, untrusting person who will assume the victimized position. From there it is almost impossible to get onto the front foot in faith and lay hold of life. He is always subjected to someone else's injustice. We must trust, love and show kindness and mercy, or we will become the opposite. If you show kindness you will be a kind person, because the Holy Ghost empowers you to do that.