The topic of the Round Table this month is casual gaming. And that's a surprisingly hard term to pin down, because as other panelists have noted people can get pretty deep into other "casual" entertainments, like crossword puzzles or office softball or thermonuclear engineering.
But this is not ultimately different from other hobbies. I watch very little television. We could say that I am a "casual watcher." It's an entertainment of last resort, usually. But I have a few shows (Battlestar Galactica, Project Runway) that I follow fanatically. Are those just not "casual shows?" (Perhaps not. Don't think about this example too hard.)
I think (and half-remembered comm texts seem to back me up on this) that we seek out media that fills a specific need, much the same way that we look for "confirmation bias" in political sources. If our needs are filled by a game more strongly, then we might play it more seriously, even if it is technically a casual game. If we don't feel that craving often, or if other options are competing for time (explaining my fluctuating habits), we might play harder games in a lightweight, fleeting fashion.
It's not that games have become more casual, or that they will do so in the future. It's that they've gotten better at accomodating both types of playing habits. The Pokemon design trend means there's more to do (although arguably it's just more tedium) with any given title, for the hardcore players. For the less obsessive, save points have become more accommodating, levels aren't necessarily as long, and difficulty curves have flattened.
The first step in the trend was the tutorial level, which nowadays both introduces the game and its controls/mechanics. You didn't have to read a manual anymore. Then there's context sensitivity (hopefully displayed with onscreen prompts) so that I don't have to remember what button does what, if I pick up a game months after the last time I played it. Alternately, there's a buttonmashing approach, where the controls are easy and forgiving enough that a new player could just mash their way through--see: Tekken. I can't stand Tekken personally, I think it's the easy reader of fighters. But for a friend of mine, it's perfect, because he doesn't need to learn any combos or special moves. He starts a game every couple of months, maybe, has fun just reacting to the events onscreen, and then shelves it again. My friend is dismayed to learn that there are high levels of Tekken play, where people do learn combos and strategies, but at least he never has to learn them.
The point is that it's not an either-or proposition. There's the potential to play many games in casual spurts, or in long, dedicated sessions. The real development has been the fulfillment of that potential.
Who else wants to talk?