It could happen at any moment. When we say "big money" what are we talking about? If I were "big money" and I really wanted to get into Bitcoin, I would be worried not so much about whether or not the price goes down more, I be worried about other "big money" getting in before me. Suppose "big money" means a person (or entity) who becomes a true believer in Bitcoin wants to invest 100 million dollars in it. There are thousands of people who could potentially do this. If a total of 100 million dollars enters the Bitcoin market in a short period of time, the price will rise well past 10,000 dollars. Now suppose big money person A comes to believe that big money person B has the same intention. It would be wise for person A to begin buying immediately at price 500 before person B starts buying, rather than wait for the price to maybe fall to 400 and risk person B buying before you. If person B buys before person A, person A will have to buy at 10,000. For a big money person who has decided that Bitcoin is a good investment, the risk of losing the race to another big money person is much greater than buying too soon, before the absolute bottom.
I am sure that big money people are already acquiring Bitcoin, but they are doing it off-exchange as much as possible and on-exchange in smaller amounts, but the time is fast approaching when this big money acquisition will no longer be unnoticed, and a stampede will occur.