As noted total resort points cannot change (with the exception that more could be added if they add new units to the resort). What they can do is shift points in that they can raise them for one season, one type of room, or for given nights, while lowering them by a like amount for other seasons, type of rooms, or nights. The impact of that is that you will always face some risk, if you purchase enough points for a given type room for a given time of year, that the points you need could go up (or down). They cannot shift points for no reason, but as long as they can explain that what they are doing is in the interests of the members as a whole and it relates to demand issues, they can act.
There have been a handful of point shifts over the years. In the early 1990's, they lowered and raised points in different seasons at OKW. There were then no changes until 2010 and 2011, when over that two year period they substantially lowered Fri and Sat night points while raising weekday points needed. They did that one over two years because they are allowed to change any one night in one year by no more than 20%, and the total adjustment actually made over two years was close to 28%. That change substantially impacted many members who had purchased enough points to be able to go five nights, Sun through Thurs, annually. Nevertheless, it was not a total surprise since both DVD and members had mentioned the possibility over many years because weekday demand greatly outstripped weekend demand. DVD had even sought possible reaction to such a change in some surveys it took over the years.
Since then there have been four changes that were all specific resort related. At AKV, they converted some savanna view rooms, including two GVs, to standard view because the rooms did not provide decent savanna views. The result is that points were lowered for the ones that became standard while the rooms in other categories increased a little. The same happened at BLT when they converted some of the lower floor theme park view rooms to standard because the views were not good. After SSR added the treehouses, the demand for them was very high including because the points for them were the same as a two bedroom at SSR. Effective beginning Jan 2013, the points needed for the treehouses went up almost 15% across the board for all seasons, while points decreased a little in the other SSR rooms. The effect of that is that treehouses are now fairly easy to book most times of the year even at 7 months out. That one obviously had a major impact on anyone at SSR who purchased when the treehouses were on sale and purchased enough points to get a treehouse annually. The recommendation to buy 5% to 10% more points than you think you actually need as a hedge against a possible future point shift did not work for those purchasers. There was also a change at Aulani which I believed had to do with eliminating one of the GVs.
When and if future changes will occur is unknown. Many have expressed concerns that certain seasonal shifts might occur sometime in the future at WDW resorts. One usually mentioned by members is the first two weeks of Dec which are currently classified in the lowest point season but those two weeks are now the highest (first week of Dec) and third highest (second week of Dec) DVC demand weeks of the year. Like concerns have been mentioned about October, which is in the next to lowest point season but is the second highest DVC demand month of the year, next to December. Meanwhile, all the spring break weeks, in the highest and second highest point seasons, are among the low to at worst moderate DVC demand weeks now.
In other words, DVD does not do point shifts without reason, but do not purchase on the assumption they will not occur.