It seems that if all those contracts expire January 31, 2042 then the use years Feb-Dec don't get an 2042 allocation.
There is no Jan UY so no worries that one group will get something nobody else gets.
DVC has not stated what will happen at the end but if you look at how dues relate to UY, my guess is that they will pro-rate the points for the 2041 UYs based on the overlap with the 2041 calendar year.
For example, for those with a Dec UY the dues paid in Jan 2041 for the 2041 calendar year cover the final 11 months of the Dec 2040 UY and the first month of the Dec 2041 UY. Assuming no dues are assessed for Jan 2042, the final dues paid cover 1/12th of the 2041 UY points so that will be all they get in their final UY. Those points will be available for stays from Dec 1, 2041-Jan 31, 2042.
Similarly, the dues paid in Jan 2041 for an Oct UY contract cover the final 9 months of the 2040 UY and the first 3 months of the 2041 UY so they would get 3/12ths of their annual allotment for their Oct 2041 UY and could use those points for stays from Oct 1, 2041 - Jan 31, 2042.
Looking at the opposite end, dues paid in Jan 2041 for a Feb UY contract cover the final month of the Feb 2040 UY and the first 11 months of the Feb 2041 UY so those with a Feb UY will get 11/12ths of their 2041UY points, usable for stays from Feb 1, 2041 - Jan 31, 2042.
Since the end date is Jan 31, 2042 and not Dec 31, 2041 it's possible they will charge everyone for the month of January 2042 and give everyone that additional month's worth of points as well.
Now if they are really generous, they will give everyone a full set of 2041 UY points despite the fact that those with UYs later in the year didn't pay all of the dues on those points but I doubt it. I think that would result in too many points left in the system and not enough rooms available for members to use them all.