this is just beginning....
Do you know something that we don't?
I think DDoS on exchanges is very common and the exchanges should have the appropriate measures to counter these attacks without affecting it functionality as well as to ensure the safety of the funds/bitcoins.
However, to be safe, we should keep most of our coins in offline wallets (paper or hardware wallets). Only those intended for trading should be in the exchanges- even if the coins are lost, it won't be 100% of your holding.