The people who are stealing bitcoins are only holding them becuase the price is not what they want they want to make the most money from their stolen bitcoins you know
and when they are selling them right now they are not making allot.
Current price doesn't matter for hackers on whether or not they want to sell their coins.
It's their first and only priority to keep the coins "hidden" and "cleaned" offline/untouched for as long as possible.
At some point in the future they will start spending/selling their coins in a manner that they don't raise any suspicions.