Even if blockchain crypto currency is not a fad (and there are many legitimate reasons why it isn’t) there simply is no way of knowing if any of these early currencies will survive. I think the market has already had a massive breakout and is trying to find stable valuation. There still is plenty of room for big gains if the currency gets more and more legitimate adoption (but right now there are significant challenges as the world’s big markets remain skeptical.
Because bitcoin has no intrinsic value, it could become worthless. I wouldn’t view any crypto as an “investment” - the rule of thumb you hear from analysts on these kinds of plays is no more than two percent of your net worth and be fully prepared to lose it. But you might also see gains, perhaps substantial.
Timing is also important. Most who bought bitcoin after October are in the red right now unless they were day trading on volatility.