He looks pretty good for that big of hole and still open. Like Mort said, infection is his biggest danger. If he has good nutrition he can get to easily it sure would help his chances.
I feel your pain. I've got three walking wounded, two haven't been seen via camera in a couple weeks so I don't think they made it. The other was still alive after the thermometer fell out the other day. I'm surprised he is still around. I didn't think he'd make it. I've had several deer that have been wounded in the fall/winter and it's been a 50/50 rate of survival so far.