Good point. If Stanis were to die, and the Northmen don't get their hands on him and Ramsey, and Stanis dosent execute him before the battle he may have a chance of survival with Asha. And what a life he will live! Cracked teeth, so all his food has to be mushed up and sucked on, he can't have sex, he can bareley walk let alone run. All his joy in life has been taken away from him. Stanis knows from Theon that the Freys and Manderlys are on their way and he tells Stanis that Ramsey Bolton will be following behind them. Whatever Theon knows Stanis will get it out of him soon, and then really what use is he. Theon told Stanis he killed the stark boys. Flint, Norrey all the North wants him dead. Stanis tells Theon that they have a warmer(fire) end in mind for him. All of Stanis Knights want him to burn. Here is King Stanis's actual words to Asha:
"Wise. I am sorry for your mother, but I do not spare the lives of turncloaks. This one, especially. He slew two sons of Eddard Stark. Every northman in my service would abandon me if I showed him any clemency. Your brother must die."
King Stanis turns to Theon wen the Karstarks are taken out to die and says to him "that is how I deal with betrayal, turncloak."
There are just to many hints in my opinion for Theon to die sooner rather than later in winds of winter. And no one is safe in ASOIAF.