The main problem i see is, people are just buying because the price is going up. Bitcoin is too expensive, so they buy some Litecoin, Ethereum and add some Ripples on top of that.
From that point of view, we're already in a massive bubble.

On the other hand, this is a global market. And unlike stocks, where you need atleast some money, this is an easily-accessible and global market where everyone can invest. How many people are invested in stocks? Probably not that high %, but everyone can and might invest in crypto.

One thing is certain, the only way is up. Through bubbles and bursts.

The technology is lagging behind(there is no production ready blockchain/tech actually...yet). But i'm pretty sure crypto is there to stay in 1,2,3,5,10 years with new innovations along the way and the speculation is what will drive it forward. It's like an alternative economy.

That being said, the current valuations are WAY too high, but then again social networks grow exponentially and crypto is spreading like plague.

So HODL is most likely still the most profitable strategy, unless you manage to time the top of the bubble and time the dip, which we know is...very hard.