I think bitcoin can reach $ 20000 by the end of this year, we can see today bitcoin prices make us all surprised with very high rise, yesterday I woke up and saw bitcoin price $ 12000 and today I see bitcoin price has reached $ 15000 what the hell with this price.
20K before the end of the year seems pretty fast to me.
But we also reached 10k quite "easily" this year.
In the end of this year it's really unpredictable because as we see the current price it isn't at stable yet, and it may rise or fall rapidly at the moment. Maybe we can appreciate that price to hit at $20000 next year and at the start of 2018 that will be the most possible scenario. We can view that price to be the most profitable price of bitcoin and that would be expected that many holders will sell when that price will become a reality.