There are people who do the job of trying to predict the future price of Bitcoin using what we call technical analysis. I dont know how they do it, I am not into it and I dont know how it works, but from what I have understood there are different strategies that are being used in knowing what the future price is going to be.
McAfee claimed that he used the same strategy that was used for predicting the bull run that took place in 2017 but still he wasnt able to predict the price for 2018 and 2019, all his predictions failed and for that he called Bitcoin the worst cryptocurrency. So, its difficult to do, but there are people who have done it accurately.