whether or not he is productive when he returns doesn't really matter and only time will tell.
The A's will not cut him because then they have to pay him anyway so they might as well keep him and see if he can earn some of the money instead of just giving it to him.
He will not retire because then he'll forfeit the remainder of his salary. No one is stupid and no one would do that. And I'm sure in his mind he feels he can come back since he's only 30 years old.