I have a thought and a question.
The thought: man, I know exactly how you're feeling with this "amazing guy, unbelievable connection, infatuation" you're describing. I've had that guy in my life, that feeling. Dazzling, isn't it? Consider yourself lucky. Many many women will never have this experience in their lives. But don't fall into the trap of thinking that this experience is a prereq for the guy you'll marry, or that this feeling is any indication of potential for a relationship. And don't sleep with him. I'm not worried about your feelings, which I think would be more or less the same either way. I just know that if you don't sleep with him, you'll increase the chance that he'll come back and visit you again. Men like the challenge and they like the idea of girls who hold off on sex. Trust me on this.
The question: have you ever had a really phenomenal relationship with a guy who considered you to be #1 from the first minute? Because a relationship like that would change your view on this particular situation. Once you've been #1 once, you're never really content to not be #1. I hate to tell you this, but right now, you're not his #1. He's flying out to see you because he probably thinks you have the potential to be, and he's also hoping to get laid, because he's male and in his young 20s and there's nothing wrong with hoping. But the two views are counterintuitive, because you won't become his #1 if you sleep with him on his first trip out. In his mind, his girlfriend is this lofty past figure who spent five years with him and was probably a virgin when they got together. She is a goddess in his mind, and she is IMPROVING with distance because her absence is probably making his heart grow fonder. He hasn't cut himself off emotionally from her, he probably still loves her, and you are going to be fighting in his mind with a myth of a girl: he won't remember any of her bad qualities.
Could he fall in love with you? Absolutely. Are you deserving of it, attractive enough for it, "right for him?" I'm sure you are, absolutely. But don't give him all the power by sleeping with him and confiding your feelings. Be the fresh, fun, no-expectation, no-pressure, sexually-hands-off girl who so attracted him once that he's flying in to see that girl again. DON'T CHANGE YOURSELF AT ALL FOR HIM.
Dana 'Big Sister' Cara