I think any market can be manipulated as long as you have the resources for it. The good thing about Bitcoin is that for years, when inflation was very high, the price was really low, and this allowed the currency to reach a larger distribution, making it difficult for the currency to be in the hands of a few, and thus making manipulation very difficult.
but i think with the passage of time it becoming more and moe difficult to manipulate the price of bitcoin. because bitcoin is becoming more famous and more and more people are accepting bitcoin as currency.
I don't think that bitcoin becoming more well known or just having more people accepting it as a currency would have anything to do with making it harder to manipulate the bitcoin price.
There are still plenty of whales out there that can manipulate the price in the way that suits them.