who know bitcoin will become in 2018 i think its not possible it become 50k USD 
This topic should be moved in the "Speculation" category.
If Segwit2x is successfull and bitcoin transactions become cheaper and faster(or even instant),BTC
will rise to 10K USD.Reaching 50K USD is doable during the next 5 years,if there are no major hard forks and no dirty government and central bank tricks(no attempts to destroy bitcoin).