If you compare the chart of Bitcoin of the Year 2014-2015 vs. Year 2018-Now, you see there is a huge overlap. Many lows and highs are similar. That means we have seen now a temporary low at $3500 and might end with a final low in March 2019 at rougly $1900-2000. This is also low of the year 2017 and might be a good retest.