Bitcoin has a market cap of 70 billion. This is very low when compared with the stock market or the gold market. There are many groups that can buy the total number of Bitcoin in circulation with a price of $4000. They can easily manipulate the market both sides up or down. Bitcoin 70% supply is stored in a very less number of wallets say 5%. Don't you think Bitcoin can easily manipulate and below $1000 is still possible?
Bitcoin can easily be manipulated but can't say that persons can easily change it's price by buying a lot of bitcoins in low or high prices (I mean group buy).
As I see bitcoin's price is easily manipulated when someone says something on it, for example when there was rumor that china was going to ban bitcoin mining and etc something similar.
Btw if bitcoin go under 1000$, then I highly believe it will damage bitcoin's reputation and kill all hope of further rise in everyone.