Making predictions about the value of Bitcoin by the end of 2018 is something like telling fortune - you will be mistaken. However, I can admit that it can reach 25K, but not 40K.
Well few people believed that bitcoin cam reach 20k by 2017 and it did. One thing with crypto is you can never say never. Prices can boom to record highs very quick, or crash in a finger snap. I'm not saying btc won't hit 40k this year because anything is possible in crypto