We can see these days that not all people know cryptocurrencies, if they do perhaps they have heard only about bitcoin, but without owning or having the experience of making any transactions.
Maybe altcoins will become popular within 3 years from now?
Maybe yes, maybe no. There's no point in guessing what will be in 3 years, that's senseless. It's more beneficial to learn the current market and prepare a strategy for the nearest 6-12 months!