Cryptocurrency Marketcap rise sustainable?

This is a question for the community out there. Is the current explosion in the cryptocurrency marketcap sustainable? Where does it go from here? We have gone from a total marketcap of $29.5 Billion one month ago to its current spot at over $67 Billion. I understand in early stages of growth in funds you will have exponential growth but these numbers seem astronomical. I also understand that compared to other markets/funds/etc Cryptocurrencies are truly in their infant stage (Gold has a $7.5 Trillion dollar Market cap)

Thoughts? Thanks for any input!