The "Proof of Keys" event is tomorrow on January 3rd.
This event is to encourage people to take possession of their crypto holdings
rather than leaving them on an exchange.
HitBTC had already frozen people accounts before this event and the fear is
that HitBTC may not have liquidity, meaning they don't have the BTC and other coins
to give their customers if too many pull their crypto off the exchange.
People have been talking that some exchanges may be frozen or die.
Frankly I agree with this idea of pulling off what they can afford to pull off
from exchanges if you can learn proper storage or holding of your keys/your coins.
I for one lost lots of BTC and other crypto on a few exchanges in the past,
and know others who have also.

People are worried it could cause kind-of a bank run and then panic.
Here is a decent video discussing it:
https://www.youtube.com/watch?v=K0qh9LfAeJU