I can see it go to 1500 in 2018 but 4000 is too much in my opinion, but this is crypto so everything is possible I guess, I am going to keep an eyes on it.
anything is possible in cryptocurrency world remember LTC grow above 400% of it initial value within one month in 2017 so dont be surprise if ETH hit a price even more than $4000 in 2018. everything is speculation so unjust might happen especially nowadays when it seems price of altcoin is being influenced. another example of this is XRP. as at today XRP is above $2 which happen within I month (December 2017) so you can see anything is possible.