Basing on the currently flow of Bitcoin's price today, I should say Bitcoin will touch $40k - $50k during the last quarter of 2018. With these rapid increase of price it would be possible for Bitcoin to hit my speculated mark, although there will be a corrections next year but I think it doesnt stop Bitcoin to continue its growth. Bitcoin is gaining more and more popularity its being widely recognized globally. There will be a huge demand in the market for the upcoming years and it will not stop increasing its value until the very last piece of Bitcoin is mined.
I agree with you, I also think 4k is achievable for 2018 and there is definitely some corrections coming. Most of the recent growth was spurred by the forks and Futures. There is one major concern though, BTC is losing its original purpose as a currency. It is being treated as a commodity now, mainly for the purpose of buying and selling for profit and as a way to trade alts. Steam have dumped BTC as a currency because of its recent instability, with it being so volatile it is very difficult for it to be used as a currency of the future. Also, the barrier for entry is too high and it is complicated for many.
I see BTC as an essential tool for trading in Crypto but I believe there is room for a new currency to crack the mass market and become a better option for use as an actual currency, for buying stuff. Time will tell though.