I didn't make a Dungeons and Dragons character with the idea that I would only play them for one session. Sure, sometimes that happened because the game fell apart or the character died horribly. But that wasn't the plan.
But now there are games like Fiasco which tells the whole story in two arcs or games like The Quiet Year or Ribbon Drive or Baron Munchausen that are clearly designed for one session. Even indie games designed for longer play, like Polaris or Apocalypse World, are still designed for a limited number of sessions.
Some of that comes purely from mechanics. You can get a game of Fiasco rolling in ten, fifteen minutes. On the other hand, you would spend hours just making a character for Role Master. (And then have them die in five minutes due to the critical roll charts. There's a reason I only played Role Master once)
But the mechanics for a short form game wouldn't exist if the demand wasn't there. More importantly, they keep on coming out which means that there is an audience for them. Possibly even a growing audience.
In the boardgames and now in role-playing games, I find that the concept of accessibility is becoming more and more important. When I first got into role-playing games in the 80s, you had to be pretty serious and dedicated because the rules were so complicated and convoluted. Now, there are games that you can pick up and play, even if you don't have years of Dungeons & Dragons under your belt.
Which has led me to another change. At least for me, I would only be playing two or three rule systems at any given time. Often, only one rule system. Games like Dungeons & Dragons or Call of Cthulhu are life style games. They don't leave a lot of room in your calendar for other systems.
But games like Fiasco or The Name of God are small enough commitments that it's much easier to put a lot of different games. That is definitely a change in how I think about role-playing games.
There is a definite switch from game mastery to game exploration. With more complex systems designed for long term, virtually indefinite play (I knew a D&D campaign that went on for over twenty years on a pretty much weekly basis), you end up doing a lot of research and, by virtue of extended play, practice. In some cases, I've seen it turn into who can use the rules better.
With short forms, it becomes about story exploration. You aren't trying to explore how the nuts and bolts work. You are exploring how narratives work. Sometimes in a comic form and sometimes in a tragic form. And, in my experience, the players are more inclined to collaborate.
I think there is a legitimate shift not just in the design of games but in their philosophy.