DVC at WDW has long had two distinct demand seasons (measured by how long it takes to usually have rooms fill after reservations open beginning 11-months out): (a) the high to extremely high demand "fall" season from late Sep through marathon weekend in Jan, and (b) the more moderate demand season the rest of the year.
The extremely high demand times during that fall season have been first two weeks of Dec, Dec 23 to to Jan 2, Tues through Fri of Thanksgiving week, the Wednesday to Sunday of the Wine & Dine race weekend during first part of Nov, the Wed to Sun of Marathon weekend in Jan, and the Thurs before Columbus Day in October through the weekend after Columbus Day.
The lowest demand times of the year (all in the moderate season) have been Feb 1 to the Thurs before Presidents Day, July 7 to July 31, the Monday after the Princess half-marathon weekend in late Feb through first week of March, and the last week of April. June has, in the past, been the highest demand month in the moderate season (but stilll significantly lower than the fall season) and May has been higher than August and Sep. Times around holidays during the moderate season also have had higher demand than other times. The highest demand time during the moderate season has traditionally been the Thurs to Sun of the Princess half-marathon weekend in late Feb, but even for that weekend demand has been lower than anything in the fall season. How extreme has the differences been between the two seasons? By example: the demand for the first two weeks of Dec has traditionally made the two Easter weeks look like a slow off-season.
There appears to be some changes in demand going on as a result of DVC's recent shift (over a three-year period) of nightly points needed for reservations by increasing them in the fall season while decreasing them other times of the year, particularly May through Sep. There does not yet appear to be a major shift of overall demand taking place, but fall has become a little less high while times in the moderate season have seen some increases. The most noticeable change in demand I have seen thus far is the increase in demand for the first two weeks of May. As a result of the three-year point shift, those two weeks have gone from being in a higher point season to the second lowest. The full impact of the point shift on demand throughout the year will probably take at least a few more years to become clear.