L.L.
I wonder rather than setting up his room exactly as it is now, if a completely different setup would be better. I know it seems strange, but that way he may not feel as though you are trying to "replace" his old room and surroundings that he is so attached to.
A couple of really good ideas are to if at all possible, after explaining that you will be going to live in a different place, that you take him to see it LOTS and if at all possible allow him to choose which room will be his very own. You could even let him help you set it up that way he feels as though he has had a part of the whole process. Also, after he has chosen which room will be his (or after you do if you can't let him), a new, really neat toy surprise waiting in his room might help to embrace the change. Those are both things (choosing room and toy)that I have read in parents magazine and a few other places. when we moved with our son, we could not let him choose his own room for safety reasons (didn't want him ont he street side of our rambler house), so I bought an entire bathroom set and did up the front guest bathroom just for him. My son adapts to changes pretty easily though...and we were moving from a one bedroom apartment. I would go over the change lots with him and try to get him to embrace it as a good thing...focus on the benefits (I know he's kind of young ot understand all that)...'what's in it for him'. Perhaps if he is exposed to the new place enough times before the move date, it will not be so hard on him.