I have yet to see where one of these types of relationships have ended on a positive note. Usually one persons winds up having more feelings, while the other just wants to play.
Hello.. I've had a few FWB in my past (going back 20-25 years), and while we are no longer sharing the "benefits" part, we are still friends. Each ended for various reasons, none negatively.. well, unless you count the one that outright lied to me. We're still friends though... so nice try.
But that's the thing I don't think he has, he is leaving to go travelling in march for at least a year so I don't think he would have a change of heart. Plus I know he doesn't want to have a relationship right now.
You know this for a fact, or you just presume this from a past conversation? Things can change over time. Either that or he's just really really comfortable with you and his more affectionate/passionate side is showing because you've grown close and he trusts you.
Best thing to do is sit down and have a conversation with him. Before you ask the questions though, make sure you are prepared for the answers. Don't put him in a position he feels obligated to lie to you to protect your feelings.