While there are aspects of this evolution that will remain, much of it is cyclical. It is kind of like music - you go from periods of 'light' pop music to serious 'heavy' music and back and forth as time goes by.
Some of the adancements will be maintained. I doubt drow, orcs and other humanoids will be considered innately evil, for example. However, I think we will see periods of shallow storytelling that fears to offend and often gives us flat or sympathetic villains (note: you can have sympathetic villains in many types of storytelling, but fearful storytelling often uses this tactic), and then we'll see a return to darkness with storytellers in movies, TV, books and D&D embracing the use of truly evil beings as villains - using horrible things to get their way.