Something else to think about - if he does say he isn't interested in a relationship and just wants sex, how are you going to handle that? Are you ok with just having booty calls?

You need to be prepared that if he says he doesn't want a relationship.... Continuing to have sex won't make him change his mind.

I'd second inviting him out with friends. Just don't introduce him as "my boyfriend" unless you know the status of the relationship. But if he agrees to hang out, and doesn't get upset if there is no sex, then it might be easier to ask.