After the bee has left the cell, we have a perfectly servicable cell. Workers will carry out a little housecleaning. Another interesting aspect of their work is that they will reuse the wax cappings used to cover the cell.
Remember, wax is expensive for the bees to create. As such, it makes tremendous sense that they will clean up the cappings that form the hole from which a bee emerged and look to reuse it. They will often move small chunks of this to a different area within the hive, building a store of wax that can be reused on yet-to-be-capped cells.