He may be gay, but I don't know how to tell him that's fine?

There is this guy I've known for 2 years. We're pretty good friends. Our friendship started out rocky because I was dating his best friend...(not anymore) But now he's one of my best guy friends.
Tons of people say he's gay. He knows that but just kinds of brushes it off and jokes about it. Personally I've always just said he's Metro. He's really into theater, arts, etc., and just generally fits into a lot of gay stereotypes.
I'm in a bit of an awkward position, because lately I've been wondering about his sexuality. (not any of my business, but he IS my friend and if he's having a hard time coming out or something, I want to be there for him.) I would love to let him know I would totally support him, but I also don't want to imply that I think he's gay, because if he is straight then that's just another person who thinks that about him, and worse, it's a friend. My best assumption would be that he is bi, but obviously I don't know.
How can I let him know I love him just the way he is without implying that I'm just another person who thinks he's gay? Should I just wait and see if he comes out? :/