South Korea has a much different demographic than the United States. Samsung plays a large part of the whole countries GDP.
Insolvent retirement is actually a fear of anyone. Primarily because you don't know when you will die. So, how long do you accept the inherent risk and start making your assets more liquid.
I really think that Baby boomers retiring isn't as big as an issue as the consumer credit market and student loan credit. It seems right now that some of the S&P's upside is the fact that its on the backs of people putting their new toys on credit cards and finance plans. I don't think that this can last forever and also the fact that the things they put on them keep on lasting longer and longer.
But, for my retirement I'm pretty long on S&P (I'm only 30 years old). I am not going to pull out at the moment and timing the market for things like that is hard for me to fathom. Taking defensive positions is more for actually Baby Boomers and people that are day trading. As you say that this correction will be triggered by Baby boomers retiring the only thing that actually counters that is medical science. I have a few coworkers in their 70s and they look and act like 50 year olds.