I'm not sure there is a whole lot you can do. I'm sure part of his apprehension is not being with his friends and having to make new friends. Perhaps you can help with this a little.
Try taking a day to visit his new school. Call the new school to find out who's class he will be placed in. Then speak with the teacher and find out if maybe you can bring him by to meet her and possibly the other students before hand. Or see if you can ask her to send out a handout to the parents of the class. Maybe a short letter from one parent to the other parents. Explain that you are new to the school and would like the chance for your son to get to meet them. And ask them to call to set up a playdate if they would be interested.
Another idea would be having a party for your son... A welcome to my new house party. You could go to his new teacher and ask if they would send home an invitation to all of the students in his class. Have cake and ice cream and games. Perhaps this way he can meet them and since he is having a fun event, the other students will want to hang out with him. Afterall, his mom will be the fun mom. ;)
Other than that, check at the local library and (if there are any) local bookstores to see if they have story times or craft times. If they do, show up to them. Also, check with the new neighbors. They may know kids his age who live nearby. Then you could walk to their houses and introduce yourselves (you to the parents and your son to the kids).
Other than those things, I think it is more of a wait and see kind of thing. Although experts say that change is easier for kids than it is for adults, that doesn't mean that it is actually easier. It, also, isn't true in every case. So just be there for him with lots of hugs and kisses and a little understanding if he would rather pout alone.
Good luck with your move. I hope that this helps out.