Is he working on recovery, or just not drinking? If he's just not drinking, then you are wise to remain on guard. It's okay to be hopeful, but be realistic as well. "Expectations are planned resentments." It's difficult for an A with no recovery plan to stay sober long term. Is he willing to go to AA? A lot of A's believe they've got it figured out, and can handle it themselves. This is usually short lived.
So be cautiously optimistic, and focus on your own recovery. I don't mean to be a downer, but sobriety without recovery is a tough one.