Sorry about your friend. It's hard to know what his chances of surviving are without knowing all of the other problems he may have. However, a rib puncturing his lung (by itself) is not particularly dangerous, and he shouldn't have any trouble recovering, assuming that he doesn't sustain bad infections (always a possibility).
If you get more information about him, please tell me, and I'll tell you more about what's wrong!
He certainly could survive. The reason he is on life support (which probably means a breathing machine) is that his lungs basically have "holes" in them right now, and he's not able to adequately breathe himself. However, assuming that the ribs that punctured his lungs are no longer puncturing his lungs (ie, they aren't in his lungs now) which I don't imagine they would be, his lung tissue will simply need to heal in the same way that most other tissue in the body does.
However, he will likely need to be on a breathing machine for quite a while. The process of healing will cause inflammation in his lungs and that makes lungs not function well... akin to a REALLY bad case of asthma (which is really just lung inflammation). Gradually, the holes will heal, and his lungs will become "airtight" again.
If he needs to be on the breathing machine for more than a couple of weeks, he may need to have a tracheostomy temporarily placed. This is where a hole is cut in his neck to all him to breathe through his neck. These, however, are by no means permanent, and he can absolutely recover from having one once his lungs are better off.
While he is on the breathing machine, he will be at great risk for infections, so will certainly be monitored for this by the medical staff. He may be on antibiotics for part of the time as well.
My opinion is, based on what you've told me, that he will survive, and probably do pretty well. But this is certainly a scary and critical time, and I would hope that he's at a good hospital with experience caring for this type of patient.