I think the main reason for the sell off was regulatory fears, especially in the US and in the upcoming G20 meeting. I think the tone from the US, EU and South Korea got more friendly in the past days. The SEC hearing went well, the South Koreans made to its political leaders clear, they care about Bitcoin and Co. and the EU want to be a leading nation for blockchain technology.
If we get a friendly regulatory environment, this could fuel more money from institutional investors, as they are hesitant because of the risks and unregulated markets.
Main risks for the bubble to pop, before they can catch up with its value are from my point of view:

1. Bad regulation (eg banning exchanges)
2. Collapse of Tether and hacks of centralized exchanges
3. The failure of a lot of ICOs (which will come in 1-3 years)
   Besides that, I truly believe this market has the potential to raise to a new asset class next to stocks, bonds, real estate and so on.