So the view that this verse is teaching that habitual sinners must never have been saved in the first place is untenable. Once a person is born again, they can never be un-born. It is a mistake to think that this verse is describing the way the unsaved behave here and now. The verse says nothing about the current behavior of believers or unbelievers. Rather, it concerns the eternal sinfulness of unbelievers.
Unbelievers die in a state of sinfulness.
Forever they remain sinners. Of course we know that they do. What is actually in view is the continued unregenerate and unjustified state of the lost. Because unbelievers upon death are sealed permanently as those who are unjustified, they remain sinners in God's sight forever. There will be no sinners and no sin in the new heavens and the new earth.