They should eventually die, but it's difficult to say how long it would take. In theory they may die more quickly if they are not dried out. If there's not a huge amount of dirt, you could try pasteurizing it if you want to use it again soon. Even if spores did survive in the dirt, they can't do anything unless they get rain-splashed or blown onto green daylily tissue.
Did the rust come with the plants, or did it just show up? If it came in on the wind from somewhere nearby then there's not going to be much you can do to stop it coming back.
