I expect ETH to continue its decline to around 7.65 mBTC by the 4th of January (EST). At that point, I expect a continuation of the cycle to bring it back up to around 8.25 mBTC.
However, after the next rally is when things get interesting. Ethereum is sitting just above the very strong 6.6 mBTC which it hasn't been below in almost a year, so I find it unlikely that this downward trend will continue for more than a month (probably less). On top of that, when the BTC rally eventually runs out of steam I expect an explosive increase in ETH. When exactly ETH will hit bottom is a little bit harder to tell at this point in time.
I'll be on the look out for signs of a trend reversal on ETH/BTC and post something if I see anything of significance.