We learn from our parents and grandparents. Young generations will continue to invest in stocks, bonds and mutual funds. There will be those who don't, but others will step up and will continue the investing game. If they don't, the economy will fall apart. The key is learning how to invest in wise ways.
Young people will continue to invest in the stock market as did older generations. During the early 2000s, we saw the onset of day traders. Many of these individuals were in their early 20s. People learned at a young age that the stock market is a way to make money. As long as individuals believe they can make money in the stock market, they will continue to invest. Age is not a factor.
With the rise of crowdfunding/crowdsourcing, young people will look to their peers for investing in not only their careers, but also to fund new businesses. There are also many less volatile and shorter term ways now to attract passive income that do not have the risks associated with the stock market.
No, I do not think young people will continue to invest in the stock market as vigorously as older generations. With the volatility of the stock market these days, I do not believe the younger generation see's the same advantages the older generation did. I believe something new (perhaps ForEx) will take over as the prime investment choice of the younger generation.