It won't happen this year, nor 2019.
I think nothing before summer '20. This downtrend has not finished yet, then we need some consolidation and slowly uptrend to get levels $10k -> $13k -> $15k... etc.
pure speculation
To be fair, it is very likely the downtrend has indeed finished. All signs point to it being finished and Bitcoin currently being in the beginning of its consolidation period in which it starts its turnaround. Look for the slow uptrend to begin before the end of the year. 2019 will be the slow uptrend back to $20k, 2020 will be the next boom.