The resort prices stayed pretty stable for a very long time. They went up and down just a bit. However, you just booked by resort and got "best available". Usually that was a very good room.
I think it was 3 (maybe 4 years ago) that they added various room categories at the resorts, including Concierge and changed the seasons. Prices, in some cases, went up more than 100%. Since then, they seem to have stabilized pretty well.
The non-WDW resorts have also stayed fairly stable. In some cases there was no change from last year, in others some nights went 5-10 points.
So, it's hard to predict but I don't expect to see a dramatic increase again anytime soon.