I think that the January won't be decisive, but the second half or even the end of 2019. Bitcoin can not soar without any reason. We need a gradual buildup, and only then, after breaking through this level, Bitcoin can begin its positive movement. This is my opinion, but many others with whom I have talked about also believe this.
This year will be a eventful and we are already seeing that in the prices where btc has crossed 4150$ as well. So good times is ahead for all of us and those who were smart would have being buying at the low of 3400$ and will continue to hold for much better price to prevail.
The price of bitcoin has taken a steep move reaching $4200, this was long expected. To the expectation now only the price has reached the $4000 range, possibly the price movement is expected to continue. Large scale investors who have made an investment a week ago would have profited good now.