Please read the passage before the commentary.
Put yourself in this context. You are expecting the second coming of Christ in your own lifetime. Some of your family or friends have died and Christ has not returned yet. Will these deceased relatives and friends miss out on the glorious second coming of Christ? If you are afraid they will miss the big celebration, then you will have a strong grief over their deaths.
Paul wanted to set his parishioners free of this excessive guilt or sorrow. The facts are that Jesus has died and has risen from the dead. All those who have received baptism have received baptism into this dying and rising of Jeus, into his death and resurrection. As Jesus has risen so also will we and are we.
Furthermore, Paul continues his catechesis, at the second coming we shall have a big parade. Those who have died before the second coming will be first in line for the parade. Then those of us who are alive will follow them and we shall all be caught up together with them in the cloud to be with the Lord in the air.
We do not know when the Lord will return in glory. When we come to sleep in death with the lord, then we shall have more information about the subject. The Lord will come and take us to his glory in heaven.