As far as I know every dorm, except for Fulton which was taken offline a few years ago, is as full as they can be while keeping the fire marshal happy. As for room availability, it can easily be forcing more doubles and only giving singles out as needed, capping the number of people who can return to the residence halls for their 2nd/3rd/4th year of college, etc. Last year, Housing was probably caught off guard with the number of people who wanted to live on campus still and the incoming freshman class, whereas this year they were planning for it and were prioritizing the incoming class or at least those that took the time to plan ahead and request the room assignment as soon as possible and not wait until the last minute.
If there was plan for a new dorm(s) to build, my guess would be on the site of the Walsh/Squires/Bek/Hancock site. However, parking for on campus students as seen from the 2024-25 year was tight, and that area doesn't have a lot of parking to begin with. I would bet if UND can get the money to relocate the College of Nursing to be next to the Medical School that would free up the area for a dorm block with parking for the dorms being nearby.