It would be a terrible thing if the Bitcoin pattern is the same as in 2013-2015, it could be the end of 2018 is only about 4000 $ -6000 $, as I think if it might happen?
Let's look at the pattern in 2013-2015 below:

and this is the pattern from 2016 to the present:

What if it really happened, give your opinion?

Eehm
it can be very much possible, if there is not enough investment made to raise the price. Unless they are going to bubble it or whatever. The previous years I can remember that the price of Bitcoin usually goes up around ending of the year and not at the start.
So as for this 2018, if Im going to say anything about this, it probably should be around the end of the year, around September or October. And after this year, the price will likely go down.
already old investors are converting their money to Altcoin or taking off their investment due to fall in the price and if the price more, the market cap of bitcoin will drop more and may bitcoin lose the first position in the cryptocurrency list. Ethereum and Ripple are behind bitcoin and it is quite sure that one of them will take over the first position in the market.