Flooring, litter box, and cat questions!

For almost a year now my bun, Weston, has had his own "room" in my walk-in closet. The door is always open and his cage is in the doorway preventing him from going in the rest of the room. He is 100% litter trained and only uses his cage as his litter box. I have carpet and I had foam flooring over that. He chewed the majority of the foam and some of the carpet. I'm going to be moving in about 6 weeks and I need to preserve the carpet in my new house. Ideally I would like to let him roam my whole room but I need to be sure he won't destroy things. At the very least, he'll have access to my new closet which would still give him space to play even if he continues to chew the carpet. He hasn't been confined to a cage since he was about 10 weeks old (he's a little over a year old now) so it would be really unfair to him to ever confine him to a cage again. Especially since his cage is his litter box--I would NOT make him sleep in that. Going along with that, I have 2 cats that go in and out of my room as they please. I monitered them with Weston for a few months and now I am completely comfortable leaving them unattended (the cats are both declawed and ignore Weston). I'm not sure if that would change if the cats and Weston didn't have a cage separating them? They know they can hop over the cage to get in the closet but they never do. I've had them all on my bed together and they get along fine. Weston likes chasing their tails and trying to get them to play. My one cat just lays there and gives him a dirty look while my other cat seems a bit scared of him and will run away from him. Neither of my cats have ever even swatted at him. I just would hate for Weston to be playing and irritate the cats to the point where they would think about biting. But I do want Weston to have more room especially since he is so consistent with litter training and the only reason he is confined now is because I don't want him chewing up something and destroying it or chewing up something harmful to him.
Also, even though he is litter trained now will that change when I move?

There can sometimes be a temporary loss of litter habits when a rabbit is put in a new area, but it doesn't usually last too long, and it really just depends on your individual rabbit.

With your cats, you'll just need to supervise until you are sure there isn't going to be any biting or swatting from your cats. Cat bites and scratches can be very harmful to rabbits, and can even be deadly, so you want to be sure they get along fine.

With his new area, just make sure to rabbit proof it. Especially carpet if he likes to chew on it, as rabbits have been known to ingest carpet fibers, and that can cause a GI blockage, which is a very serious problem. So as long as you prepare his new room for him, there shouldn't be too much of a problem.

Can you use an ex pen to confine him and keep him separate from the cats? I don't trust any other species to be left alone with my rabbits. Next year one of my new roommates is bringing cats with her and I'm planning to just keep the door closed between them when the bunnies are out.
Declawed cats can be more likely to bite (because they no longer have weapons on their paws) so do be careful of that since cat bites are really nasty for bunnies and humas alike.

I would expect him to mark new territory when you move, possibly with urine but definitely with feces. Try a litter box in every corner until you figure out which corner he likes best.