The total # of points for the chart can not change. DVC can adjust the chart and make certain days more points, but somewhere else they have to decrease the # of points. My understanding is that this has only happened once, over at OKW. Some people who've been around here a bit longer might have a more detailed answer on that for you.
The points for non-DVC resorts/trips can (and have) gone up over the years. There was a big jump in WDW resorts when they changed the booking option, however, they are now staying fairly steady.
There was a change at OKW in 1996. Essentially they adjusted adventure season up, particulalry for GV and weekends, then made minor reductions throughout the rest of the year to even it out.