TFA has some interesting stats, but not much narrative to go with them. I would say that there are two big over-arching themes that are driving changes behind "who plays games".
1) The first generation to grow up playing games is now moving into its 30s and even early 40s. Moreover, while this reflects my personal prejudices only (hey, at least I'm upfront about it), I suspect that with many of the first generation of gamers being academic and nerdy types, they are disproportionately well-paid now compared to their wider generation. So the people who grew up with games in the 1980s and early 1990s now have a lot of spending power. For some years now, the 30-40 year old age group has been the most lucrative in gaming.
This is partly why Japan's importance as a market for (as opposed to a producer of) games has plummeted. Aside from "quick blast on the train" mobile games, gaming in Japan is in a very unhealthy state. Domestic production in Japan, when it targets domestic audiences, increasingly plays for children (eg. Nintendo), teenagers (Capcom) or the unemployed/under-employed "otaku" demographic living off its parents' income (Gust, Nippon Ichi, Cave etc).
This is largely because Japan doesn't have the market of relatively well-paid adult gamers that the West has. Some of that is down to social stigma (games being a "kids' thing"), but much more of it is down to working cultures. Maintaining a middle-class lifestyle in Japan requires the kind of office-hours that would make even a Western games-development house in crunch-time blush.
So yeah... in the Western gaming market, oldies increasingly hold the purse-strings, while Japan is increasingly falling out of the mainstream.
2) There is no longer one single "games industry" any more. If... indeed... there ever was. Back in the 1980s and 1990s, the games industry split neatly into two halves marked "console" and "computer", with very little cross-over. These days, that distinction has almost vanished (most console games bar first-party exclusives come to PC, Valve increasingly act as the platform-curator for the PC). But at the same time, there is a growing divide between "core" and "casual" gaming, with the latter not looking much like traditional gaming at all.
Facebook games and mobile titles like Candy Crush Saga draw nothing but contempt from "core" gamers (including many of those affluent 30-40 year-olds mentioned above). But they have drawn in a vast market which would never touch a "core" game - and that market is heavily female. So the demographic of the gaming population in general is skewing to reflect that.
There's also what almost constitutes a third tier somewhere in the middle - the "dudebro" gamer (which is overwhelmingly, though not entirely, male). These are the guys who spend a lot of time gaming, but almost all of it goes into Madden/FIFA (delete as appropriate depending on whether in the US or not) and Call of Duty/Battlefield (delete as appropriate depending on favoured brand of spunkgargleweewee). This is a big demographic, but as MS learned when it pitched the Xbox One at them heavily, it isn't a big-spending demographic or one that's particularly sensitive to technological advances.