Hi L.,
I would suggest that you explain to him as much as you can, in simple language. Talk about the move often. Small children learn through repetition, so get him used to the idea of moving, what that means, what he can expect, what his new room will be like etc. If you raise your expectations of him, he may rise to the challenge and surprise you. We had a similar situation when my son was 2 years old. From the time my son came home from the hospital, he shared a room with my daughter (two years older than him). He had never known things any other way. When we moved (to another state) the children got separate rooms and I worried about how my son would react, since he idolized his big sister. At the new house, he got a new "big boy bed"(full size bed) in addition to a new room all of his own. To my surprise he was delighted, with having his "own" space, he never slept better and not even the first night did he have issues. He loved spending time in "his room", I would find him playing in there and he decided that he did not like having a night light and that he wanted to sleep with the door closed. So give your son the opportunity to rise to the challenge of being informed about what is happening and what he can expect. I had also made a small photo album of our old house, his room from different angles, all the other rooms, the staircase, the front of the house, etc. I never used the photo album, I was prepared for a hardship, but it never came. I explained to him what was going on, what I expected from him and got him involved in the process (helping pack his things). For us it worked out better than I could have hoped for, so I say new home, new space, go for the "big boy" aspect and but his bed in his new space. Most importantly be Happy about His Bed in his New Room, weather or not you are really excited about the move, make it a positive experience for him and it will be a positive experience for all.
Good Luck