I made posts like this before but here it goes again.
I think virtual worlds will change everything. They will become so big in the future that you will still be able to play what seems like a single player RPG, completely story driven, no other players in your way, etc, but it will actually be within a virtual world and there are other people in other parts of that world playing together. So it is an MMO that can be played like a single player game too. Yet whatever an individual does in their single player experience, will have a lasting impact on the world as a whole, even after they have quit and moved on to something else.
The games will be focused on the worlds themselves, the people (players) and their interaction with the world. It will be more like a MUD but as a virtual world. The only game I can give as an example would be EVE. But basically you will log in to a virtual fantasy world, but it will enormous, not just a bunch of WoW sized continents, instead it will be comparable to Earth itself. Many large regions procedurally generated but with incredible detail, all procedural. There will also be cities, towns, dungeons, harbours, outposts, prisons, all kinds of locations that are crafted by the designers, in a world with many races and factions that have various alliances and hatreds of each other. It will behave like a real world, AI characters will behave far better than they do today, some will go about daily routines like an improved Skyrim Radiant AI, but some will be born bad, and will commit crimes etc. Guards or bounty hunters will capture them, they will face trial, and be imprisoned, and everything including the judge and jury will all be handled by AI. It will be a living breathing world, ships travelling across oceans with goods to sell at a distant port, there will be virtual people who work at the docks and live 24/7 a real life. They will have a name and a family and background, they will wake up, get ready for work and head to the docks etc. It will be just like the real world, many thousands of characters who behave just like real people. Their routines will even vary, based on illness, weather, mood, etc.
Living amongst these people and this virtual world, will be millions of real people. There will be full time traders, crafters, builders, all kinds of types of gameplay will be catered for, all in the same world. This is already done in a lot of games but it will be on a far bigger level. There will be money lenders, professional bandits, professional painters, bards, ship builders, landscapers, everything you can think of.
You will be able to head to dungeons and search for lost treasure, but that will be the most simple form of gameplay in a game that has so much more. You will start with nothing and build up, and eventually you will travel with some friends and find a dungeon, maybe it contains a valuable mound of crystal. You play for weeks and eventually kill everything in the dungeon and can claim it as your own. You hire people to come and mine the crystal for you, and you start transporting it in caravans to a distant city, and in time you become rich. You then build an outpost in the middle of the journey to store resources for the journey (food etc), and also to house some soldiers to protect the caravans. In time you will be able to grow that to a village, and then a city. In time you or your group of friends will be the mayor of a large city, and that can continue to grow and become an empire, and you could be come a king or a part of a council. But the world is a big place, and there will be others who may want to ally with you, or may want to destroy you and take everything you built up. Maybe they want to capture your city and make it their own, maybe they want to raise it to the ground.
Virtual armies will fight, and virtual corporations will compete as well, sometimes in criminal ways.
Gameplay will advance as well. Virtual Reality will become the norm, currently the resolution isn't perfect and some other issues, but in 50 years it will look as good as real life and run smoothly without even having to spend much money on it. It will be very lightweight, and completely wireless, and there will be no sickness from it. There will be things you wear that push and pull you and make you feel more connected to whatever is happening to you within the game. There will be a wide selection of accessories too so you no longer need to play sitting down, although you could if you wanted. It will have a full body tracking, so lazy asses can sit and they will look like they are sat on a horse. Others can walk and run for real on 360 degree treadmills that feel just like walking or running in real life.
Melee combat will be done for real, sword swipes and blocks will all be done by the player and people will go to night school to learn sword fighting and old combat techniques that they can use in their favorite virtual worlds. But in addition to the physical act of swinging and blocking with weapons, there will be complex magic, stances, special abilities, that will all be controlled with brain waves. This is already possible in a basic form, but in 50 years you will be able to activate something by just thinking about it. Living in a virtual world and doing all this stuff virtually, will barely feel any different to living in real life. There will even be ways to earn real life money from the virtual world, in the same way that there are gold farmers today, but it will become a lot bigger and lot more legitimate.
Also there will be a lot more joined up industries within gaming. Currently there is SpeedTree, and some other stuff, and Unity which is a big framework. In the future there will be entire game mechanics that can be bought and placed into a game, or outsourced to be created by a professional company that creates bespoke game designs. So the Bethesda of the future will decide they want to make a space game, and will buy the universe from a company who specialises in just creating virtual universes. Then they will buy some gameplay specialist services, and the whole thing will be built in a semi-open source engine. The game devs of the future will be more about designing the whole.
These types of games will be on a whole different level to others. There will be new terms to describe them, but only mega multi billion dollar corporations will make these huge games. There will also be smaller companies that make more niche games, like what we have today with the indie devs, but they will be far bigger and better, serving many different niches.