I wonder if we are going to see higher manipulation than whatever we are feeling already about it but whales only do what is needful for their business and smaller buyers or individuals have to follow them by the chart. If you notice a huge buy in the chart that means to expect more buy and price will appreciate and that follows down too. I don't think institutional buyers are going to be a problem with the bitcoin behavior.
The whales always rule the market, it's a fact that you see in every market. Let's say, for example, we have some wallets addresses that have bitcoin locked on them for many years that has not been moved by the real owners, the moment the private key owner desire to spend from thus wallet always create this fear among holders and speculators that the early birds are trying to cash out, the whales will want to sell at the top and use the opportunity to buy at lower price maximizing their hodl and that's how the fear will naturally create a panic sell in the market.
Again, of what used is Bitcoin to institutional if they don't have the chance to buy on low price and if the price of Bitcoin doesn't go up over time, try will do whatever they feel is good for them as long as their money is involved.