What?? for just $12k the bitcoins could dump for such amount? if your worried then the answer is no since the amount is not big to get panic with and if you are been fud by the people who tell you that then listen to the people here since we will give you a clear answer and the amount could cause huge dumps are ranging millions of dollars before the price move.
12k btc is just 112+M on current price and as said this one isnt enough to make some dump in the market.There might be movement but it would just typically be considered as a usual movement on btc price.As i have read up where these coins are already partitioned or transferred into smaller parts which means tracking of these coins would already be impossible.
Stopping it from getting sold wont be there yet exchangers are free ways to encash these hacked coins.Same as usual!
After separating them into small portions, of course, they won't have such an impact on the price as if scammers had decided to sell everything at once. For sure it would also be difficult to sell everything on one exchange, because if they did, then on this exchange drop to $5k would be 100% sure. Selling 12k BTC at once on many exchanges, may not cause such a large price drop, but it would certainly cause panic and this panic could lead to a decrease of up to $5k.
The possibilities will be on different exchanges, but I think before they dump it they should use btc to buy different coins before they'll able to be successful on their motives. However this situation isn't that confirmed in actual scenario, speculations kept raging with this idea. It still depends on how a certain individual manage to take this, and having any panic can be controlled as long as you learned the reality of everything in cryptocurrency.
I know that sounds abstract with such a huge amount, but still is possible. 
