I want to add to this discussion.
What about hardware? Will we always have game systems bringing out new versions every 2-3 years? Ex. Will we see the Playstation 6 in 2020?
Will it be like my grandmother who kept her old rotary phone until she died 5 years ago?
While other people are sitting around in the nursing talking about how much fun hiking and climbed used to be, I’m still gonna be sitting at the table slinging dice and making Rod of Lordly Might jokes.
Stay with it, bro. That guy that’s always one spot above the bottom? That’s me. I’ve still never called in a nuke on MW2, and the only EMP I’ve fired off was part of an (well, it was mine) emergency airdrop. And yeah, MW2 is the most recent FPS I play.
I think you’re pertty much doomed to lose hand-eye coordination with age, and the fast-action games will get less popular with the older crowd simply because it sucks to be everybody’s favorite target. You can favor a sniper class all you want and pretend you’re just trying to be stealthy, but in your heart you will always know you don’t have the agility to be the “run & stab” demon.
Which leaves strategy games. And if Elder Scrolls in 20 years is as much better like Skyrim was to Daggerfall, I’m pretty sure it will be deadly frightening to old folks. 
Different kind of gaming, mate.
Uh, we don’t have game systems bringing out new versions every 2-3 years NOW. The Playstation 3 launched in 2006. The PS4 launched in 2014. That’s a bit more than 3 years.