That price prediction is very popular among many investors and Llew Claasen did not predict anything new,maybe he just read what Michael Novogratz said a few months ago that
Bitcoin could 'easily' reach $40,000 by the end of 2018If you just think about it and if all the facts are taken into account then 40 000$ is not something hard to reach.Last year show how nothing is impossible,from 1000$ to 20 000$ was amazing progress.So if todays price is go up just 4 times, 40 000$ will be realized.
What definitely should not be forgotten is a correction that will most likely follow next ATH, and it can be 50% more or less.