V.W.
Some kids are just more sentimental. My own son is a lot like that. He even wanted to keep our old dining/breakfast table (that the surface of was ruined from his toddler antics) instead of getting the nice new one. When we finally got ready to take it out of the house, he laid on top and asked me to "at least take our picture with it" and succeeded in getting his younger sister to whine about it, too. They were 10 and 7 years old!
This is what I would suggest: Take your son on photo shoot of your current home, and let him take pics of whatever he wants (or let him direct what YOU shoot photos of, lol). You could even take pics of the view out of his bedroom window! Then help him organize it into a little scrapbook that he can keep in his new room.
He may just not like letting go of things. With a scrapbook, he won't have to let go completely. My son is very sentimental about such things, and 'worries' that he will "forget" them. Having photos can help a LOT with that worry.
(FWIW, I did take 2 or 3 photos of my kids with the dining table... and they have never asked to see them. When they came across them one day while scrolling thru my digital photos on the computer... they both laughed hysterically about the whole thing. But the act of taking the pictures alleviated their sense of loss AT THE TIME).
Good luck. He will be fine... just the anxiety of the "moving process" might be more to blame.