there is no guarantee that things that happened in the past months or years can also be happening next year in almost identical manner but data we can gather from the past can be serving as a guide on probabilities and that is why we can be creating some models. It is like predicting the future based on the past though again there is no formula that can exactly tell us what can be though this is much better than to just wildly guess the possible outcome. We have to always remember though that Bitcoin has this habit of being unpredictable at times so we should not be shocked to see some good and even bad surprises along the way leading to the scheduled having in 2020.
The thing that I just know is that every year of bitcoin is always better than the previous year, so I am not afraid of bitcoin tomorrow, provided that I dont invest at peak period, then all these fluctuations that we see now are just child's, play, when the real bull run comes, we will see less of decrease and more of an increase in the value of bitcoin and in the value of our investment.
I do not even stress myself predicting bitcoin since I am not much of a regular trader, I buy bitcoin when its down and then hold till there is news of bull run when I can decide to sell my coin at the goal price that I have set for myself. The bull run of bitcoin will come, there is absolutely no doubt about that, we just need to keep our fingers crossed and keep watching as things really would unfold.