Having been there, here are my thoughts. I dated someone for three years, and I am sure she would have labeled me commitment-phobic. The unfortunate truth was that while I loved her and really liked being with her, I was always wondering if there was someone else who would be better for me. The comfort of being in the relationship was strong enough that I couldn't break up with her. To make a long story short, after one of our commitment talks she finally broke up with me; and while we were both heartbroken, we were also relieved. Two years later, we were both happily married to other people.
I won't go so far as to say that he can't be changed. But you are going to have to level with him and give him a choice. As comfortable as the relationship might be, it is going to hurt more (and you will feel angry about having wasted so much time) if you let him drag this out for months or years with no intention of making a commitment. So tell him how you feel and where you stand. Find out what his goals are. Does he intend to get married some day? If not, then you have your answer. If yes, then at what age/has he thought about kids, .... At that point, you should compare his time-frame with your own. If they don't match up, then it is time to move on.
The harsh reality is that when a guy is able to commit to being in an exclusive relationship but afraid to commit further (after a reasonable amount of time), it usually means that he is not sure about the relationship.