User blog comment:TomWelling/How is that possible?/@comment-176.249.115.102-20121211175537/@comment-5102537-20121211222053

They won't. Uther appeared for the very last time in "The Death Song..." and it was confirmed that Lancelot won't return at all.

I suppose the horn will be some kind of a horn that starts an attack/a war, and that's it.