Carol, I think, will be kept around for some time. She helps bring out a different side of Daryl, whether he wants to show it or not.
Hershel dying seems likely, but that's because I can easily see him of just dying of a heart attack from all of that stress. They'd still have to cauterize the wound and somehow prevent an infection. The point of cutting off his leg was to prevent the fever from occurring, but I think he's a goner regardless.