Well its very difficult to predict that whether bitcoin will fall, be stable or will increase in 2018 middle to last as bitcoin is an unstable form of currency so its value keeps on fluctuating a lot. But. As bitcoin has gained a lot of users and its popularity among people is increasing daily because of which bitcoins demand among the people is increasing very much. This is also evident from the increasing price of bitcoin so its safe to say that bitcoins price can increase.