If God saves them from their sin, then they will have no sin when they enter into the kingdom, and will have been cleansed.
Again, there will be no sin in God's kingdom.
Rev 21: 8. But the fearful, and unbelieving, and abominable, and murderers, and whoremongers, and sorcerers, and idolaters, and all liars, shall have their part in the lake which burneth with fire and brimstone: which is the second death.
V-27 And there shall in no wise enter into it any thing that defileth, neither whatsoever worketh abomination, or maketh a lie: but they which are written in the Lamb's book of life.
JH :-)
Their sin may be forgiven, but they're still sinners, right? They are still capable of sin even after being saved. Just like an alcoholic is always an alcoholic, even if they've been sober for 10 years.