Depends on how many more coins the dumper is willing to dump. Right now, in the last hour or so, it's been close to 20,000. Now, if I was trying to manipulate the market to get more BTC, I'd probably dump some on Wednesday and Thursday, nothing major, just to get a downward momentum going. When miners and others who own hundreds of coins start selling them into the market out of fear or need, I'd wait till they're likely to have started their withdrawals from the exchanges, say Friday afternoon or so... then dump the whole motherload, drive the price down to almost nothing, and buy back without them being able to jumpstart me.
But then, I don't try to manipulate the market...