The Gods have a plan for Lorgar, I'm sure of that. If they wanted him to lead the Black Crusades he would, but we'll just have to wait and see what they want with Lorgar. Like tabbytomo said, it would be very cool for him to come back with the other Daemon-Primarchs and kick Loyalist Primarch butt in the end times.
"Death? You want death? I'm afraid that would be far too boring."