The introduction of a new gamer demographic that may or may not be more profitable does not determine which genres survive or fail, or what kinds of gaming are focused on in the future. What determines which genres survive is the ability of developers to produce games that attract enough support to recover their development costs and turn a healthy profit. What (really) threatens "hardcore" gaming is the insistence that all "hardcore" games take full advantage of the processing power of the most powerful systems around, which (dramatically) increases development costs and threatens the profitability of these games.
Besides that, I think we really need to question what people mean by "casual" games. I have heard many people imply that "casual" games are too easy, and yet many JRPGs are considered "hardcore" games even though you only need a pulse to complete the game.
