Help! Boyfriend may go away...what to do?

My bf is thinking of joining the air force. Weve only been dating about 4 months. I think the military would be good for him, because I think it might serve his desire to see the world and also give him a way to finish school. However, I'm 25, and want to have a family before too long. I wouldn't have an issue if we had been dating longer, but am hesitant about committing to something exclusively with that sort of instability and distance when we don't know each other all that well yet. Would it be fair to ask him if, if he goes away, it would be okay to continue dating/writing/getting to know each other and possibly re-solidifying the commitment at a later date but also see other people for a bit if the opportunity presents itself? I care for him a great deal, but am also not willing to put my life on hold for an indefinite period of time until he figures out what he really wants. Thoughts and opinions?