That is actually a pretty good analyses and I even agree with their price range, although for different reasons. I think the top was already in, but let's give a chance to have a double top in the 18K-22K range. That would be my highest guess, but only if it can clear the 16K line.
On the low side, vertical charts correct 40-60% from the top. BTC already did 45% and I think 60% is in the cards, so that would be 8K. In between those values there will be lots of volatilities, gains and loses. So they are probably right about the 4 crashes of 40%.
Now this is just the chart talking. If we throw in the fundamentals, well, they don't exist anymore, and bitcoin's days as the king of the cryptos are over. 2017 showed that the king has no clothes, forking or starting a new crypto are easier than to achieve consensus for invention. There are governments selling off huge amount of bitcoins, the tether thing will probably blow up, and we are long due for a major broker being hacked/going bankrupt.
Competition is heavy and better than BTC. HFs can now invest in it via futures, thus the futures markets are also sucking investors' money away. Adoption is shrinking.
By the end of 2018 it will be lower than on January first, but how we get there will be interesting.