The unrepentant sinner is to be put out of the church so that their sin won't influence others to sin. And that they might repent and stop sinning. Notice that they will be saved in the day of the Lord Jesus. Which is when Jesus returns to earth. There is no salvation for the backslider at death, but  is available at Christs return to earth, on the day of the Lord.

1 Corinthians 5:5 KJV

To deliver such an one unto Satan for the destruction of the flesh, that the spirit may be saved in the day of the Lord Jesus.