I don't think Ayu's career will ever be "over". As she's said before, if she cannot go on singing, she will continue writing songs/composing for other artists. Though I really do wish Ayu would take some time off to rest as well. She really needs it. Her voice isn't horrible to listen to for me, but it's not as good as it was even in 2006-2007.
When I saw CDL 09-10, I'm sorry but when she was grunting through About You, I kind of felt bad because she sounded...tired, or not into it. She should go back to New York for training and just relax at a spa somewhere for a few months, rejuvenate and get back out there kicking butts!