Last year I had a deadout- I set it back in the woods to deal with at another time (procrastination is my middle name). It was robbed very badly and the remaining bees starved- yes, many dead bees- heads in the cells ect.
A couple months later (well, ok, I had forgotten about it) I stumbled across it...and it was booming! A swarm had moved in and was really going to town. I inspected it and it was clean. Turned out to be a great producer..in fact, one of my best last year; an amazing thing since it was a first season swarm. Hive is still going gang-busters now, even in winter. So, yes, they will clean up the mess.