For all the talk about millennials preferring bitcoin and other investments over stocks, the co-founder of popular stock trading app Robinhood expects equities to stay in favor.

"I wouldn't say that we're anticipating a massive shift from stocks to cryptocurrencies," Robinhood co-founder Vlad Tenev said. "We don't see the equities market going away anytime soon."

Stocks are at record highs, but digital currencies have run up even faster this year to their own all-time highs. Although talk of investing in digital currencies and the transformative force of blockchain has grown, many still see more conventional investments and technologies winning in the near term.

Just like the dot-com boom of the 1990s took more than a decade and a market crash to produce Facebook, analysts say, the cryptocurrency world still faces many growing pains.

Tenev's optimism on stock trading is notable, given that 78 percent of Robinhood's more than 2 million customers fall into the so-called millennial category, those ages 18 to 35.

The conventional thinking is that these younger investors are less interested in stocks than they are in bitcoin.

A Bankrate survey in July found that just 13 percent of younger investors like stocks, while real estate and cash were tied first place among millennial investors at 30 percent each. A separate poll conducted in August by LendEDU found that more than a third of U.S. investors ages 18 to 34 said they plan to invest in bitcoin.