I mean, it really depends. Gold n Silver will never go to zero, save for some apocalyptic event where only true, usable commodities are valued. I think it's important to distinguish cryptocurrencies and the underlying blockchain tech. What's valuable to know is in many cases, you do not need the cryptocurrency to benefit from blockchain technology. In fact, I think there are plenty of utility tokens that simply do no need to exist, but exist for the sheer function of raising capital. So while I don't think blockchain technology will go away, cryptocurrencies might experience a heavy consolidation phase where coins with no realistic utility are weeded out.