Bitcoin's price have skyrocked over the past year so it's difficult to discern the fundamentals that can help figure out its future value. Its value is raising up and down from one to another day. Furthermore, the way Bitcoin has been breaking through all previous expectations has rendered any attempt at using technical analysis to make Bitcoin price predictions for 2018 irrelevant. Nevertheless, there are a few factors that affect the cryptocurrency's price going forward.
Rate of adoption: The value of a network increases as the number of users on said network increases. This also applies for Bitcoin.
Technology: Although Bitcoin is built on Blockchain technology, it is somewhat inferior from a technological perspective to other cryptocurrencies built on the same platform.
Other competing cryptocurrencies: With more and more digital coins surfacing up like Ethereum, Litecoin, Ripple and so on, the argument for using Bitcoin as a means of transactions is becoming less justifiable.
The use of futures: Creating a futures market for trading Bitcoins will have a profound effect on the young currency.
Overall u can't really predict the future value of Bitcoin's. These are only a few factors that can influence the value of them.