If mining difficulty continues to increase with a rate of 10 % or above ,I dont think the price will decrease below $ 400 soon. Whenever a stability is about to come on mining difficulty, its more possible to see a price decrease.
With this difficulty and the block halving incomming we won't stay below $500 for more than a month, from now. It's a good moment to buy right now or to hold if you already have enough Bitcoins. It's easy profit.