I suspect that DVC will give you the points for that last use year, and then "allow" you to try to use them until the end of your UY at other DVC resorts. So, if you get your December 2054 UY points on a resort ending in January 2055, you can book your home resort until January 2055, but they will likely give you until December 2055 to use them at another DVC resort.
Of course, DVC could also play hard ball and tell you that you have the points, but you only get 2 months to use them. That would, however, put them in a very bad position with DVC members who were considering buying new, as well as what the press would say about it...