After the peak, Bitcoin dropped three times to the zone of 5800 to 6400. That was not surprising considering the parabolic rise in price from ~$1000 to $19,500 in the last year. As mentioned before, this is 70% fall and if we were to look at the historical crashes both of them followed a parabolic rise there is still room for correction.
I think about $6k is as low as it will get, I do not see it going to $4k like so many people believe. For bitcoin to go down as far as $4k there will need to be thousands of bitcoins sold at once to cripple the market and other people panicking and selling like crazy.
I do not see how anyone can have thousands of bitcoins and sell it at these prices when bitcoin is so low. It happened only once when mtgox trustee who is probably the only person that has that much bitcoin and still can sell without a worry did it but never been done ever since. So, I think we are at a place where there is no one else left in the market even whales that would be willing to sell that much bitcoin at this cheap prices, hence the only way is up for bitcoin.