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..
It looks very possible for ethereum to reach 1000usd level in January 2018. My expectation is that ether will hit 1K and will struggle around that level for some time as it was struggling around 500usd level in the same way.
We don't know what we do know is that the volume of transactions is 3 times more than bitcoin and that the technique of Ethereum is the best of all. We also know that if you take this in consideration that eth is heavily undervalued. We will see huge ETH Volume and rise the coming year.