Yep, loosing drinking friends is inevitable when you sober up. I'm not even sure they were my friends when we were drinking together. I just kept buying rounds and they all hung around me. After 4 years of sobriety, I don't see any of them?..
I'm hanging out those boring ones. You know, the ones that don't drink..lol.
Seriously, don't fret over this. When he's ready to quit, he will. In the meantime you have you're life to save. Just don't drink. Nothing is worth drinking over. Nothing.