Casuals are the people who keep systems alive. Look at all the best selling games late in the PS2's life. Many of them are casual games such as Guitar Hero and Singstar. Why do casual gamers keep the system alive so long? Casual gamers care least about graphics and system power.
The PS3 lost the casual gamers this generation. I don't them regaining those customers with the PS3 at this point. The PS2 never had to regain the casual gamer.
Anyone can guess. It takes no effort to throw out lots of predictions and have some of them be correct. You are not and wiser or better for having your guesses be right. Even a blind man can hit the bullseye.