Without doubt I belive that ETH in January will reach to 1000$ but u can invest to different altcoins that can give u more profit, because price of ETH now is too high u can buy any altcoin with low price..
Yup now it's $700 and next month it will cross $1k price, But you will not get more profit in this coin. ETH is good for a long time investment. Instead of this, you can buy other altcoins, and you invest same $700 you have a chance to double your investment in just 1 month. I hope next month all altcoins will take charge and go high.