Last year, Bitcoin started at $3,531 by August 11, 2017 to $19,248 in December 17, 2017. That's 445% growth in just 4 months. Last August 11, 2018, Bitcoin is being traded at $6,194 USD and it will only need 222% growth to hit $20,000 by December 2018. That is just half of 445% growth last 2017. So if question is to hit $20,000 by December 2018, it's very much possible.